Intermittent ABS/RSS Problem

[Cadillac Jim]

A couple of weeks ago I went through a deep muddy puddle in a construction area and my brakes were wet and my ABS wanted to take over a lot. A couple of days later i checked the codes and found RSS codes C1783 and C1785 and cleared them. They came back in a day or two, along with TCS code C1255. I decoded to leave the codes this time for the snapshot data and have it looked at with the next oil change, which is due now. Today, after starting the car hot and driving along, I saw the ABS and TCS dash warning lights on and checked the codes. I got the array of codes below. After a mile or two the lights went off, the first two codes went to HISTORY and I got TCS data again.

PCM

P1602 Loss Of EBTCM Serial Data

IPC

U1040 Loss of Class 2 Communications with ABS

TCS

C1236 Low System Supply Voltage

C1255 EBCM Internal Malfunction (ABS/TCS Disabled)

C1298 PCM Class 2 Serial Data Link Malfunction

RSS

C1783 ICCS2 Data Link Left Output Short Circuit to GND

C1785 ICCS2 Data Link Right Output Short Circuit to GND

When fault was active, both ABS and TCS lights were on, P1602 and U1040 were CURRENT, and TCS output was NO DATA; the rest were HISTORY. After it went away, all codes were present and HISTORY.

I did a search on C1783 here on Caddyinfo and found several cases. It seems that the common denominator in the solution of all of them is a bad connection in the ignition switch, specifically circuit IGN3. I'm in no mood to get into a parts-switching jubilee if this is something that I can troubleshoot and fix myself. Any comments would be appreciated.

Interesting old threads:

http://caddyinfo.ipbhost.com/index.php?showtopic=20227&view=findpost&p=138312&hl=C1783&fromsearch=1

http://caddyinfo.ipbhost.com/index.php?showtopic=20032&view=findpost&p=137539&hl=C1783&fromsearch=1

Etc.

Any comments are welcome. I have an appointment to have the oil changed Monday and an independent mechanic will look at it. I'm afraid that if this is a wild-goose-chase type of thing, as the C1236 hints, then it probably should go to a good dealer who will check the voltage on IGN3 and change the ignition switch while I wait, rather than torturing a perfectly good mechanic and myself. My mechanic uses a well-worn aftermarket PC-based code and data reader, not a Tech II. He diagnosed a cracked cat element once by noting that the waveform at the rear of the cat mimicked the wavefront at the front of the cat too closely.

[Ranger]

I'd check the connector at the EBTCM. Pull it, spray it down with some Brakleen and blow it out. That deep mud puddle you drove through might have something to do with it.

[JimD]

A couple of weeks ago I went through a deep muddy puddle in a construction area and my brakes were wet and my ABS wanted to take over a lot. A couple of days later i checked the codes and found RSS codes C1783 and C1785 and cleared them. They came back in a day or two, along with TCS code C1255.

My approach to any and all diagnostics is to use the KISS method. And my knee jerk points me at the "deep muudy puddle" first and foremost.

Your "C" codes have the EBTCM in common. Given that the EBTCM is located at the bottom LH front corner of the engine cradle, where it is exposed to all the crud that can be splashed up from the road surface, my first step would be to inspect the chassis wire harness and EBTCM connectors for damage, corrosion, and all the other water-induced possibilities.

[Cadillac Jim]

Yeah, the first line of defense should be the EBTCM. I'll check it tomorrow. In particular, I want to see if the connectors, the mounting screws and seal are OK and tight. It's designed to take that kind of thing.

'll do what I can to check the path through the BATT 3 (not IGN3, as in one of the threads and my initial post here) fuse, the OFF-RUN ignition switch circuit on page 8A-10-2 and the first of two 10 Amp ABS fuses. There are three RSS fuses, two 10 Amp and one 20 Amp, in the trunk compartment fuse block but these would be long shots.

I think that the real news is in the FSM process for DTC C1236, pp 5E2-94 and 95. This DTC is set if the speed is over 5 mph and both the battery and ignition voltages are below 10.5 Volts. This is probably the highest voltage that will set an insufficient voltage DTC. Since it was 107 F out at the time, and the car had been parked very hot for about 15 minutes, this could be a heat-weakened battery, nothing else. This goes back to the ABS fuse, but the 50 Amp Brakes fuse voltage is sensed, too.

At no point in the FSM do I see anything on C1783 or C1785, but these are clearly the normal force data links between the EBTCM and the CVRSS module in the trunk (diagram on 5E2-17, also on 8A-43-0), and probably reflect shorting at the EBTCM connector (diagram on 5E2-19). These go through C101 (as does power to the EBTCM) which is in the engine compartment fuse/relay center according to page 8A-201-4. Connections on C101 are on 8A-202-0 and include lots more than that so I expect that C101 is OK.

The first thing to do is to check the EBTCM connector, which is under the air cleaner box according to the EBTCM R&R instructions on page 5E2-214 and 215.

[tdcrash63]

Be very careful with brake cleaner and electrical connections. I myself have damaged connectors and pins. I use cleaners designed for electrical connections and test on a small area before.

[Cadillac Jim]

Over the last month the problem has gradually worsened. At this point the syndrome is that the ABS and traction control lights will come on for a few seconds. If you read the codes while they are on, the ABS will give a NO DATA message. Afterward there usually are no ABS codes. RSS C1783 and C1785 occur constantly, and I have caught them as CURRENT a number of times.

All the fuses on the relevant circuits in the underhood and trunk compartment fuse blocks are OK and there is no visible corrosion. My meter shows good voltage and continuity on all the fuses and circuits.

Today I changed the ignition switch because it seemed that the ABS and traction control lights would extinguish when I touched the ignition key. No change in the problem.

Friday, appointment to check under the car for electrical problems and, failing that, to get an exchange EBTCM module.

[Warspite]

Be very careful with brake cleaner and electrical connections. I myself have damaged connectors and pins. I use cleaners designed for electrical connections and test on a small area before.

It is much safer to use DeOxIt 5, or any other Electrical contact cleaner (heck, it used to be called "Tuner Cleaner" for rotary TV dials). I use it for vintage audio gear, and anytime I disconnect anything in my SLS as part of repair/replace.

Good Luck!

[Cadillac Jim]

My mechanic has the car on a grease rack and has a bunch of schematics laid out, and is checking the wiring harness out now. If nothing is found and the module has volts, grounds, and connections, it comes out for an exchange unit.

The change of ignition switch did do something: I could no longer clear the ABS and TCS lights by touching the ignition key. So, the ignition switch *was* scratchy, and maybe causing an occasional code, but wasn't the problem with the ABS and TCS lights coming on and staying on for anywhere from a second or two to several minutes. That problem has been getting steadily worse and now happens at least once every time I drive the car.

I'll know tonight if there is a problem with the wiring or connectors. The module will be an exchange unit, so I expect that it will be a few days into next week before I get it back if that's where this is going, and it appears that indeed the module has an internal intermittent electrical problem.

[Cadillac Jim]

THE PROBLEM IS THE MODULE

My mechanic verified that all the voltages and grounds up to the module were OK, so we agreed to replace the module. A local dealer wanted $1024 for the module. I remembered prices of around $600 online so I went to check. What I found is that this module is AC/Delco part number 16265346, listed by RockAuto for $583.99, GMPartsGiant for $599.78, and by NewCadillacParts for $687.18. An outfit called Standard Motor Products offers a rebuilt one for $146.79 plus a $60 core charge -- actually a return-and-rebuild service -- but I decided that I wanted a new GM part.

GM HAS BACKORDERED THIS MODULE

RockAuto lists this part as a non-stock item with 5-day shipping, but I decided to go with them anyway because of their reputation, and I couldn't reach anyone by phone to verify shipping so I didn't really expect to do better. I tried to order this from RockAuto and got an out-of-stock message and called them. They told me that this was because their web site did a check with GM and found the part was back ordered, and they don't take orders on that basis. As you know, parts for old cars sometimes aren't available for months from GM or other manufacturers. Module part number 16265346 is only for the 1997 model year. GM will accumulate orders from dealers and others until they can justify a production run, then the part will be available for a few more years. This goes on until demand no longer will pay for the set-up to make a production run. I ran into this with the mufflers when I was rear-ended a few years ago. Even Borla gave me a 90-day availability date.

ORDERED A CLOSE-OUT STOCK ITEM WITH A SHORT WARRANTY

RockAuto has a few available in a warehouse that they are letting go for $301.79 (GM cost to them???) with a 30-day warranty. My mechanic tells me that this module rarely fails, and that most people with older cars like mine will simply "drive with the light on" rather than make such an expensive repair, so traffic in this part is just about zero. I can envision a bill on the order of $2K or more if this car were taken to a dealer by a clueless owner, because of the diagnosis time (it's intermittent!!!) and the $1K cost of the part, and the possibility of being charged for the valve assembly -- a $2K part, so I can see why this might be so. So, I figure my best option is to get the genuine GM part and worry about replacing it should it ever fail again.

WATCH THIS SPACE

I'll update after I get the car back, in about a week and drive it enough to be sure what's happening (think: Labor Day). Also, I get the old part, and I will take it apart and find the problem, and post pictures here.

[Cadillac Jim]

CLOSURE, PHOTOS TO FOLLOW

The problem *was* the module. I got a warehouse close-out, 30-day-warranty item from Rock Auto for $309.99, including shipping (I just checked and the same part is now listed by them at $329.79) and my mechanic installed it for under $200, which included electrical troubleshooting to eliminate wiring problems before we bought the module. The dealer wanted over $1K for the module, pricing that apparently covers things that a DIY (ior my) mechanic buying across the counter does himself.

I replaced the ignition switch because 99% of the time I found that touching the key would turn off the ABS and TCS lights and cause codes to go to HISTORY instantly. After changing the switch, I found that the ABS/TCS lights, codes, and messages came every so often anyway but touching the key wouldn't affect anything anymore. Thus the ignition switch was a little scratchy and pinged the module, waking it up out of its increasingly frequent zombie trance.

I have photos of the new module, and of the old module, both not taken apart. I will take apart the old module and find any visible evidence of problems that I can and post everything on this thread. Expect it by the weekend.

If you see C1783 and C1785 and the RSS, ABS, and other fuses and voltages are OK, it may be the first sign of failure of the EBTCM module. I've seen several postings of this on Caddyinfo on searches, but most don't have closure posts at the end of the threads. The best ones found that it was the ignition switch, but most had problems with other circuits on the same switch or fuse, like the turn signals. In my case, I started getting C1783 or C1785 or both every time I started the car, nearly always as HISTORY (read: good voltage after bad). The EBTCM module has two large relays on th exposed side, and one smaller one or a MOSFET ground for each of the solenoids on the valve module. I count 12 of them on page 8A-44-0 of the 1997 FSM. If one of the large relays is for the pump motor and the other one is for the power to the valves, the second relay could be going bad. More later, after I take it apart.

EDIT: Whoops, it happened again, after the better part of a week of no codes. Full EBTCM off-line event. I'm not taking the old one apart because it's apparently not a bad module. Stay tuned.

[Cadillac Jim]

Over the last six months the problem has gotten steadily worse, to the point that I sometimes get "STABILITY REDUCED" or "TRACTION OFF" right as I back out of the driveway. It never goes more than a mile before something happens and it throws one code or another.

My mechanic had it and couldn't get it to malfunction - cold on the rack. He did try moving around the wires on the connector. But there are a couple of things that lead me to believe that it's the connector backing out:

• Nearly always when I get an ABS or TC light the diagnostic mode gets NO DATA from the TCS module, e.g. the EBTCM. When the codes go away, there are no TCS codes.
• Sometimes the EBTCM survives the event and preserves codes C1282, C1236, C1255, C1298, etc., all of which are known to be thrown by low battery voltage - or low voltage to the EBTCM.

Thus I think it's losing both 12 Volt feeds through C1, the side of the connector with the big lugs. I'll also check grounds G107 and G110 on the front of the block, and, if I can, the ground on the back of the brake pump motor.

My mechanic doesn't want to work on it until a warning light comes on and stays on. This will never happen, but often the TCS and ABS warning lights flicker asynchronously like a light show. Any change, such as taking my foot off the brake, an engine RPM change, putting the IPM into the diagnostic mode, the IPM interrogating either the PCM or the EBTCM for codes, will cause a change.

I called my dealer and wanted to talk to my service manager; the call was fielded by the mechanic that used to work on my car. I quit letting them service the car because this same tech kept trying to get me out of the car; there were some suspicious events, and I caught him skipping an oil change that I was charged for - and he stonewalled the whole thing: "Its OK now." after I had topped off the oil myself. He yelled at me for ten minutes.

This weekend sometime I'm going to pull the EBTCM connector myself. It's accessible to a younger man once the air cleaner assembly has been removed. I'm going to give it my best effort, with a can of contact cleaner, two bright lights, a pair of needle-nose, etc. If I don't get it either because I physically can't get my head in there or the electrical demons elude me, I will give it to my mechanic again. If he can't get it, a dealer - not my old one, but a dealer at least 30 miles away - gets it with a $500 limit before they call me with diagnosis and authorization. A call without a firm diagnosis and estimate with Goodwrench lifetime warranty gets a NO. If that happens, I will trade it. I think this is the most likely outcome.

If anyone has anything helpful to add, let me know.

[rockfangd]

you will be shocked then you disassemble your old unit. Steel and aluminum parts dont mix well.

I have done many of the GM kelsey Hayes units. They are good on the inner fenders but have lots of problems after awhile when mounted on the frame or subframe.

309 is not bad at all. I have trouble finding them for under 600.00. Please do posst pics and further info, and I must also ask how are your brake lines?

Did the new one come with new bushings and bolts?

very important to dampen vibration and noise from the motor

[Cadillac Jim]

I replace my module with a new AC/Delco with the same part number six months ago. It was OK for two weeks, then the codes slowly started coming back.

I have my old unit right here, and have been using it with the FSM and the codes to try to figure out what is happening. The connector to the EBTCM is, apparently uniquely, not listed in the FSM section 8A-202. I've put together a pinout by connector and pin number from the schematics for the ABS/TCS, which I will use in spite of the fact that the pin numbers aren't anywhere on the module. I'll fill in the pin numbers and get the full diagram when I have the connector in-hand by using the wire colors and my pinout.

What irritates me is that I can't persuade my mechanic to simply pull the connector, clean and reseal it, and put it back. I'm going to have to do it myself.

[rockfangd]

the pin nubers are not on the unit, hey are on the plug. Honestly I hate to say this but I would cut a harness in a salvage yard and reference the pins that way. I made up a harness with a wire to hook up to the battery to cycle the pump that was not working. pinouts are not easy to find on thi

[Cadillac Jim]

I'm about to go out and do it. The job is actually simple, according to the FSM. You pull the air cleaner box, then you can see it and reach it. You pull the retainer pin (which, I will bet, is not fully inserted to lock the connector in place) and you gently work the connector off.

This is where I will have problems, with getting a light in-place and determining which terminals are pushed back into the connector, which ones aren't tight, etc. I will likely have a problem getting any lens in my trifocals to get me a clear picture and will likely resort to my macro lens and twin-lite with my SLR, which can get details that no human eye can see anyway. I believe that there is a 80% probabilty that the EBTCM is losing power, so I'll concentrate on the two big red wires and their terminals.

Here's what I have from the FSM:

FSM Order C1/C2 Pinout Color Function

1 C2 3 WHT IPC Antilock Indicator

2 C1 E RED Battery, BRAKES Fyse 50A

3 C1 D RED Battery, BRAKES Fyse 50A

4 C1 A PNK Ignition, ABS Fuse 10A

5 C1 B BLK Ground, G110

6 Bolt BLK Motor Ground, S130, G107

7 C2 9 BLU Brake Switch Input

8 C2 24 BRN/WHT Traction control On/Off Switch Inpu

9 C2 25 ORN/BLK Requested Torque PWM (to PcM)

10 C2 6 TNA/BLK Delivered Torque PWM (to PCM)

11 C2 10 PPL Class 2 Serial Data (to PCM)

12 C2 26 PPL Data Link Connector

13 C2 22 BLU Lateral Accelerometer Input

14 C2 27 GRN/BLK Sensor Ground [Lateral Accelerometer, Yaw Rate Sensor]

15 C2 11 GRY/BLK Signnal reference (5 Volts) [Lateral Accelerometer, Yaw Rate Sensor]

16 C2 21 DK BLU YAW Sensor Input

17 C2 20 LT GRN Digital (SWPS) Phase A

18 C2 4 LT BLU Digital (SWPS) Phase B

19 C2 18 BRN Left Normal Force (to CVRSS)

20 C2 2 LT GRN Right Normal Force (ro CVRSS)

Pardon the format loss; this is cleaned up from a clipboard copy from Excel and the tabs turned into single spaces as did the line feeds. But you see that this, reordered by pin number (the order is that given in the FSM schematics, and is by function), gives the colors for all the wires that are used, so it will take about two seconds, once the connector is in sight, to get the terminal numbers and letters.

Note that G107 is one of two on the front of the engine, and is the higher of the two. This also grounds the radiator fan motors and relays, and is a high-current ground. If it was bad there would be other codes, I believe, but I'll check it anyway. G110 is another matter. If that ground is bad or intermittent, that could cause all my problems. I don't think it is because the RSS codes I'm getting are C1783 and C1785, and if the ground was bad I'd be getting C1782 and C1784. Since the EBTCM is losing its codes it must be losing its power, so, if the ground is good, then it's losing the battery power. I've long since checked and changed/swapped the BRAKE fuse and I know that's not the problem. So, I have a bulls-eye on the terminals for the big red wires.

Give me a few hours to get it all done.

[Cadillac Jim]

I had my hand on it but could not remove it from the EBTCM. There is a plastic cover over it that is clamped on. I couldn't get that off, either.

With the air cleaner housing off, you can see the module, the manifold with the motor on the back and the connector. The manifold is facing the fender, and the module is bolted firmly to it facing the center of the car. The connector is on the far side, leaning over the fender, and it's under and just to the rear of the left-hand cooling fan. It's clear that to get even poor acccess to the connector that the top cover, dog bones, top radiator hose, and fan/relay assembly must be removed, not just the air cleaner. It was all I could do to get a macro lens in there, much less my hand. I had to remove the flash heads and work one of them in over the top radiator hose to illuminate the connector for a decent picture, albeit from a bad angle.

The connector seemed to be on squarely, but I couldn't tell how tight. The true tale there is told by removing the cover and seeing if the locking pin is pushed all the way in. Even if it is, there could be dirt and even water inside if the seal isn't really good.

If the problem is with the connector, I moved it enough to make some kind of change. If it's different when I next use the car, then I have verified that the connector needs to come off.

[Cadillac Jim]

I did establish that it's a loose or backed-out connector to the EBTCM. Yesterday I make a quick shot at pulling the connector and found that you could just see and reach it with the air cleaner out of the way, but that the upper radiator hose and probably the cooling fans were in the way of actually pulling the connector. I did pull it onto the EBTCM with my hand as best I could. Then I put everything back together and reconnected the battery ground cable.

This afternoon I got in the car and everything was perfect. No codes, no messages. Until I hit a rough road. Then, the EBTCM went offline. Another bump, and the TCS and ABS lights went off and everything was OK - until I hit another bump. Etc.

It's pretty clear that the locking pin has backed out and the connector has pulled away from the EBTCM. With everything that definitive, all thoughts of trading the car go away. If my mechanic still can't bring himself to pull the connector, I'll do it. I would rather pay him than drain the coolant, pull the radiator top cover, pull the cooling fans and relays, drain the cooling system, pull the upper radiator hose, pull the air cleaner housing, and climb in there and deal with that nasty connector in awkward, dark, close spaces myself. But I'll do it if I have to. And, I know that it will fix the car.

[rockfangd]

guess I am lucky witth long skinny arms, it helps alot and cuts steps ;p;

[Cadillac Jim]

OK, my mechanic called GM and they told him that this was almost certainly the wiring harness. The connector is off and looks good, and none of the lugs is backed out. The locking pin was present and pushed all the way in. The main culprits are the big red wires, the redundant power lines for the EBTCM on pins D and E of C1, the six-wire big-spade part of the connector (two aren't used). C2 is the 30-wire pin-connection part of the connector.

GM tells him that I need the under-hood wiring harness, the one that connects to the EBTCM - and many, many other things. This is because the big red wires from the Maxifuse block are routed along with all the other wires back over the bell housing where the breakouts to all the H2O2 sensors and the transmission are, then back to the front where all the other sensors and breakouts are, and that a lot of intermittent problems like mine have been traced to this harness in the past.

How do I get this harness? Does anyone have a part number, or a source? PM me for the VIN if you need that.

[Cadillac Jim]

Please, if anyone knows how to get a new or used engine harness, the one with the EBTCM connector, for a 1997 ETC, speak up. My mechanic has a dealer parts department searching, and I've been looking online, with no luck so far. If we all come up empty, this is the end of the car.

[Texas Jim]

Please, if anyone knows how to get a new or used engine harness, the one with the EBTCM connector, for a 1997 ETC, speak up. My mechanic has a dealer parts department searching, and I've been looking online, with no luck so far. If we all come up empty, this is the end of the car.

Jim,

This is a parts guy from my other Cadillac forum...

He has been real helpful getting members parts...

Wouldn't hurt to give him a call...

His name is Chris...

Chris Heath (RippyPartsDept) is an ASE Certified GM Parts Consultant at

Rippy is a Cadillac, Hummer, Saturn & Saab dealership - family owned and operated in Wilmington, NC since 1946

We offer all forum members deals on parts and freight - e: parts@rippyautomotive.com

ph: 800-RIPPY-22

[Cadillac Jim]

Texas Jim - yes, that did it, Rippy's parts guy Craig found for in something called the "legacy warehouse" and gave me a staggering but not unexpected price, but also another surprise - this harness goes through the feed-throughs under the car, clear to the rear, or at least to the electronics complex behind the rear seat. Cost to change this harness is about 15 hours flat-rate. Craig recommended that I try to repair the individual circuit first.

[Texas Jim]

Texas Jim - yes, that did it, Rippy's parts guy Craig found for in something called the "legacy warehouse" and gave me a staggering but not unexpected price, but also another surprise - this harness goes through the feed-throughs under the car, clear to the rear, or at least to the electronics complex behind the rear seat. Cost to change this harness is about 15 hours flat-rate. Craig recommended that I try to repair the individual circuit first.

Glad I could help.

Wow... 15 hours to replace the harness....

I never would have thought that.

But I am glad he found it for you... JUST IN CASE you do need it.

[Cadillac Jim]

This is a whole-car harness, connecting everything from the PCM to the PZM behind the back seat, and going through all the body feed-throughs.

Because of the high price of the harness and installation, the repair cost will about equal the KBB estimate for the price of my car. So, my mechanic recommended a local Cadillac tech and the dealer that employs him has agreed to ask him to look at my car in the morning. With Goodwrench connector breakouts and individual circuit testing facilities, a tech an troubleshoot a harness and replace individual circuits as needed. We will go this route if it can be done.

Interestingly enough, Chris said that there are two other areas that I will be looking at before 200,000 miles: the engine and the suspension. I told him that I already have a Jasper. He told me that the OEM struts may not be available much longer; I mentioned Monroe, but he was not knowledgeable about aftermarket parts. He did say, when I asked if Monroe was OEM, that GM has a part specification and may change vendors from time to time, which is of course very true. My mechanic showed me an Arnott strut for a Caddilac that he had for installation on another car, and showed me the wires and solenoid for the RSS; it is less expensive than the Monroe, he said. I just checked on Rock Auto and the AC/Delco strut assembly is down to $645 (L) or $687 ®, and the Monroe is down to $395 (L or R). Looking on the Arnott web site, I see passive struts but not active struts, though.

[KHE]

Jim,

I wouldn't worry about the suspension components - A bit of humor: at the price of the OEM units, I doubt they sell very many of them so there should be stock available for a long time...

I believe Monroe has direct fit active shocks but they are still pretty expensive.