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P1602 Loss Of EBTCM Serial Data

U1255 Class 2 Communication Malfunction (Serial Data Line Malfunction)

C1738 Exhaust Solenoid Valve Short to GND

C1762 Left Rear Position Sensor Input Fault

C1783 ICCS2 Data Link Left Output Short Circuit to GND

C1785 ICCS2 Data Link Right Output Short Circuit to GND

You didn't say whether any of these codes were CURRENT or HISTORY, or what your driveability problem is. Also, the codes are reported by module; it can be helpful to say which module threw the code. Most codes can be thrown by only one module, but some, like U1255, can be thrown by *any* module. If you have no problems and all of the codes are History, reset the codes and drive for a day and see if any of them come back.

The P1602 and U1255 can happen to any car. If they don't come back quickly they can be ignored. If you ever see one CURRENT, it's indicating that there is a real problem. Sometimes when these codes show up along with certain other codes, they can tell us something.

C1738 refers to the solenoid on your leveling in the rear. When you turn the key on in a quiet garage, you will hear several different sounds as the car "wakes up" and one of these is the compressor that keeps the rear end level. If this code is CURRENT, the wiring is shorted, or the solenoid is bad. I think that the solenoid is part of the compressor assembly.

The C1762 probably means that the level sensor on the left rear has a loose connector, or that the link from the suspension to the sensor is loose or off on one end, or missing. The level control can't work without it, and it may cause other problems too, perhaps with the ABS, RSS, traction control, and Stabilitrak.

The C1783 and C1785 refer to links between the EBTCM and the RSS. The RSS provides suspension road force data to the EBTCM over these links. [esoterica not in FSM] These links can occur if the battery voltage gets below 12 Volts while the EBTCM is working, say, stopped at a light on a hill with the headlights on, the EBTCM can stop and throw these codes along with a U1255. [/esoterica not in FSM] If they are History and they don't come back quickly after the codes are cleared, you can ignore them. If they do, the first thing to look at is the battery cable (clean between the three copper connectors on the positive cable, and, if necessary to get a tight connection add a copper washer from the auto parts store) and have the battery load checked; the next thing to check is the alternator. The worst case is that you may need an EBTCM module, but don't go there until you are sure it's not just a low battery voltage thing.

To answer your question "What do I do?" you should check the codes again to make sure that none of them are CURRENT, and you should look at the level sensor on the left rear to make sure it and its wiring are OK, and also check the wiring to the level control compressor. Then, reset the codes, drive the car for a day, and check the code again - while the car is parked and idling, before you turn it off. Once you turn off the ignition, all the codes go to HISTORY.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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U1255 - Serial Data Line Malfunction

C1738 - Exhaust Solenoid Valve Short to GND

C1762 - Left Rear Position Sensor Input Fault

C1783 - ICCS2 DL Left Output Short Circuit to GND

C1785 - ICCS2 DL Right Output Short Circuit to GND

I "THINK" the bottom two are related to the EBTCM.

I assume your SERVICE RIDE CONTROL is on...

Both of them "MIGHT" be caused by the U1255.

Both the left and right outputs communicate with the EBTCM thru the datalink...

Someone else that knows more about it, will have to chime in here and help.

EDIT...

Thanks Jims_97_ETC

You did a lot better explanation than i did.

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I have P1602 ,U1255, C1738, C1762,C1783 and the C1785 codes what do I do

Too many codes! Have you powerwashed the engine bay by chance?

The saddest thing in life is wasted talent

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Yes the codes are current and no I did not wash the car. Thank you for the help but, i'm still confuse the trunk won't get down neither and the idle is playing and the engine wan't to stall.

when you press the trunk button in the cabin do you hear the solenoid for the trunk latch click (it's loud). all other controls to close the trunk are independantly controlled by simple switches & mechanical sensors on the trunk latch itself, so there are no other interactions with your previous post. You did not provide detail on the trunk issue so it's tough to provide any more. you can start by making sure there is no sand, dirt, or such on the "square" contact points on the latch.

Have you had work done on the car recently? - seems alot of things have come at once. how is your voltage reading? - have you had battery issues recently? Was the car sitting for a while? - we need a little more background on the car too. how long have you had it, what other issues did it have etc.

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I would start by washing the bottom of the car with a hose to make sure that road salt isn't shorting some of the wiring harness under the car. If the codes are still CURRENT when it dries, start with the easiest: the road level sensor.

If the U1255 is thrown by the IPM and C1783 and C1785 are all CURRENT, then your EBTCM is not working. Check the connector. If it's corroded, make sure that the big tar paper road debris shield under the radiator is present and in good shape because the EBTCM is protected from road salt and debris by this shield. If your battery voltage is under 12 Volts, these codes may go to HISTORY when the battery is fully charged.

If road salt isn't the problem causing the C1738, and the wiring is OK, then you need to replace the exhaust solenoid on the leveling compressor.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Ijust got the car, the battery was dead so I change it and problem start. The guy told me the traction/abs was not working. But he told me the idle was going good and did not want to stall. When it's cold it's fine I can start it no problem I go take a little ride and if I turn off the engine I have to put the gaz pedal to floor to start it and he want to stall in park.

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First, the level sensor on the left rear is bad, if the C1762 is CURRENT, and you need to fix that. Usually it's a connector or a loose or missing link and is easy to fix. That code, when CURRENT, will cause the traction/ABS light to come on, and the light should go off when it's fixed and the code goes to HISTORY.

Having to floor the car to start it when hot means that the fuel injection is flooding. On a Northstar, flooring the car with the engine not running turns off the fuel injection so you can clear a flooded intake manifold, much like a carburetor (which won't give the car gas at starting speeds if the throttle is wide open unless the choke is stuck closed). If that is happening, the most likely culprit is the fuel pressure regulator (FPR). This won't throw an OBD code. You can check it by pulling the vacuum hose off of it and seeing if you smell gasoline.

The U1255, C1783 and C1785 could be due to a low battery. If the traction/ABS light still does not go off, give the car a chance to run with a fully charged battery before you look at these codes.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Does anybody know where are all these part. Or is it a good idea to buy the cadillac manual at Canadian tire.

And Thank you to every one I will try those thing and reply. Your help will help me pretty much. And by the way how I can clear all code I'm just able to clear the pcm code. Thank. Sorry for my bad English but I'm French and I do my best

Edited by qwertyu22
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Yes, you do need the manuals.

The recommended one is the Cadillac Service Manual by HELM

You can buy them directly from HELMINC on the net or you can find them pretty cheap on ebay.

The Chilton or Haynes manual is really no good for you.

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Does anybody know where are all these part. Or is it a good idea to buy the cadillac manual at Canadian tire.

And Thank you to every one I will try those thing and reply. Your help will help me pretty much. And by the way how I can clear all code I'm just able to clear the pcm code. Thank. Sorry for my bad English but I'm French and I do my best

Just pull the vacuum line off the FPR at idle (red arrow) and look for fuel leaking from the nipple. There should be none.

post-9-129980755298_thumb.jpg

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