derbybug350 Posted April 13, 2008 Report Share Posted April 13, 2008 Hey guys, Im new to this site and have spent the last 4 hours reading the very interesting questions and replies to the various topics. I have yet to find an answer to my problem though. My caddy has an intermittent no start problem that is driving me nuts. It didnt start AGAIN last night after work and the driver info panel stated " service fuel system". This has happened several times. The engine will turn over for ever but not fire. I am a heavy truck/bus diesel tech and am very skilled in the mechanical field but cant find any info on this problem. I am beginning to wonder if the ignition cylinder is starting to go bad and the sensor in the switch occasionally doesnt read the pellet on my factory keys correctly, therefore shutting off the fuel pump relay. I cleaned the pellets on the keys today to no avail. Last week the car wouldnt even turn over and the driver info panel stated " security error wait 5 mins" or something to that effect. I waited the 5 mins and the car started and ran fine. I pulled the codes today and I got the P0231 code for the low voltage on the fuel pump circuit. I hooked up my Snap-on scanner and it said that the fuel pump relay was inactive(OFF). I checked the fuel pump fuse and its fine. The relay is new and operational. What is malfunctioning to shut down the fuel pump relay? Would it be the BCM(body control module)? I cant find any info on how this security system works and cant test each module individually with my scanner. I went to the library for a couple hours researching ALLDATA.com and found the diagnostic chart for code P0231. When i got back to my car to start the diagnostics on that, the car started right up(like there was nothing wrong) maybe I hold a grudge longer than my caddy does but this is starting to piss me off. I want to get to the bottom of this before I get stranded some where where I cant walk home in the 38 degree windy rain that I did last night (on friday of all days too. Sorry this is so long but I want to be as complete and accurate as I can. ANY info or suggestions would be greatly appreciated. Thank you and I will be helping and replying to others on this site as I find it very interesting and helpful. Thanks, John Link to comment Share on other sites More sharing options...
adallak Posted April 13, 2008 Report Share Posted April 13, 2008 First, welcome to caddyinfo.com! Looks like you have both security issue (wait for 5 min) AND fuel pump issue. Bad pellets are possible, the other culprit might be the wiring inside of the ignition lock cylinder. Those wires are known to break gradually. Some day you will get stranded when they break completely. The security system disables rather the starter than the fuel pump, as far as I know. Can you hear the fuel pump for a few seconds when you turn the ignition key ON (engine OFF)? There are several identical relays which can replace the fuel pump relay. You might want to play with them to see if it helps. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
derbybug350 Posted April 13, 2008 Author Report Share Posted April 13, 2008 I have replaced the fuel pump relay and then checked it when the car wouldnt start. My scanner states that the fuel pump relay is disabled when it doesnt start. I have listened for the fuel pump and it doesnt make any noise when the relay is disabled. My scanner also gives me the fuel pump voltage reading and it is at 0 volts when the problem is occuring. So my thoughts are that the security system is malfunctioning and causing this. When I got back to the car yesterday after letting it sit for almost 2 hours, the thing started right up. Im going to look at it again this morning and test the fuel pump relay circuit now that I have the values of the terminals from the flow chart I got from ALLDATA.com (which is an awesome web site. You can access the same info that the dealers use for diagnostics at your local library on one of their computers) I think that the wiring or ignition cylinder is the culprit here but dont want to tear the steering column apart when the problem is elsewhere. Link to comment Share on other sites More sharing options...
JimD Posted April 13, 2008 Report Share Posted April 13, 2008 I do not have the schematic diagrams for your year-model but some of this might be usefull. GM/Cadillac's philosophy on security is to use the PassKey logic to disable the starter circuit. The fuel pump circuit is controlled by the PCM. The pump should run for several seconds (priming) at KEY-ON, ENGINE OFF. The pump will be turned on again when the PCM sees crankshaft and camshaft position sensor pulses indicating the engine is spinning faster than xxx RPM. The presence of oil pressure is used as a backup means of enabling the fuel pump circuit. Sounds like you have two separate issues that just happened to show up at the same time. Murphy's Law proven again. Jim Drive your car. Use your cell phone. CHOOSE ONE ! Link to comment Share on other sites More sharing options...
KHE Posted April 13, 2008 Report Share Posted April 13, 2008 My guess is the security system wires to the ignition switch are fatigued and are making intermittent contact. When the car won't start, the security system is disabling the fuel pump - that's why there is no voltage at the fuel pump relay when the car won't start. If you don't want to tear into the column, there is an easy workaround. Measure the resistance of your ignition key pellet and then buy some resistors at Radio Shack that equal the resistance of the key pellet. You might need to put some resistors in series or parallel to obtain the correct resistance. There is an orange wire that comes from the column that looks like a phone cord. It will have two small white wires inside the orange jacket. That is the harness to the ignition cylinder. You can unplug that and insert the resistors into the vehicle harness side and the car should start. Once you verify that, you can cut the ignition side of the harness and solder the resistors to theignition side and plug it into the vehicle side and the problem should be solved. I had the same issue with my Fleetwood Brougham about four years ago - I replaced the ignition lock cylinder and had the new cylinder re-keyed to the original keys. I made a "cheater cord" from the old ignition lock cylinder harness and resistors and keep it in the trunk so the next time the cylinder wires fail, I won't be stranded. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
adallak Posted April 13, 2008 Report Share Posted April 13, 2008 My guess is the security system wires to the ignition switch are fatigued and are making intermittent contact. When the car won't start, the security system is disabling the fuel pump - that's why there is no voltage at the fuel pump relay when the car won't start. If you don't want to tear into the column, there is an easy workaround. Measure the resistance of your ignition key pellet and then buy some resistors at Radio Shack that equal the resistance of the key pellet. You might need to put some resistors in series or parallel to obtain the correct resistance. There is an orange wire that comes from the column that looks like a phone cord. It will have two small white wires inside the orange jacket. That is the harness to the ignition cylinder. You can unplug that and insert the resistors into the vehicle harness side and the car should start. Once you verify that, you can cut the ignition side of the harness and solder the resistors to theignition side and plug it into the vehicle side and the problem should be solved. I had the same issue with my Fleetwood Brougham about four years ago - I replaced the ignition lock cylinder and had the new cylinder re-keyed to the original keys. I made a "cheater cord" from the old ignition lock cylinder harness and resistors and keep it in the trunk so the next time the cylinder wires fail, I won't be stranded. My wires went south finally when I was far from RadioShak. I cut the wires, and installed the spare key on the car side to fool the security system. Just made a temporary resistor from the spare key, and later replaced it with a resistor from RadioShak. There is a list of resistor values Cadillc uses on those systems. You do not have to match the exact value, jut get close to it. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
derbybug350 Posted April 13, 2008 Author Report Share Posted April 13, 2008 Hey guys. When I got to the car again this morning, it wouldnt start. Fuel pump relay was off again. I tested the relay wiring and followed the flow chart until it said to replace the relay. I know the relay is fine! A quick way to determine if your relay is good or not is to swap it with the one for the horns. If the horns work with the fuel pump relay in it, then your relay is good. The horn relay is just below the fuel pump relay when you remove the plastic cover for the fuse/relay block on the left wheel well. Anyway, when i tapped on the steering column and tilted it back down to where I have it when driving, and guess what? The thing started right up. I think the problem is in the wires in the column for the ignition switch. They are probably getting worn and making contact somewhere in the column. Im 6'4" and always tilt the column to exit the vehicle. I think at this point I would rather try the fix that you suggested and put some resistors in the switch harness to bypass the key pellets. Where is the harness connector located? Is it at the bottom of the column near the knee booster panel? That sounds like a great way to solve this problem and I would like to give it a shot. If I cant match the exact resistance of the key pellet, would you suggest getting resistors that provide a little higher resistance or a little lower resistance? Im thinking a litter lower but not sure which would work. Thanks again for your help!!!!!! Link to comment Share on other sites More sharing options...
derbybug350 Posted April 13, 2008 Author Report Share Posted April 13, 2008 Oh yea 1 other thing I forgot to mention. I tried to bypass the switched ground at the relay to bypass the fuel pump relay being shut off via the PCM but that didnt work. Maybe the designers at GM thought of that when they designed this system. Link to comment Share on other sites More sharing options...
derbybug350 Posted April 16, 2008 Author Report Share Posted April 16, 2008 Does anyone have an idea of where the connector for the wiring harness for the ignition switch circuit is? Link to comment Share on other sites More sharing options...
KHE Posted April 16, 2008 Report Share Posted April 16, 2008 The connector to the ignition switch security contacts is below the steering column - you need to remove the lower black panel on the driver's side. Look around until you find the small, flat orange jacketed cable with two small white wires and a two position plug. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
derbybug350 Posted April 20, 2008 Author Report Share Posted April 20, 2008 Hey KHE I found the orange wiring harness with the two white wires in it . I couldnt find the connector anywhere before the 30 or so pin connector to the vehicle side harness so I cut the wires and placed my resistor in place. Now I get a "starter disabled due to theft system" message and the thing wont turn over now. Any ideas or suggestions?!?!?!?!?!?!?!?! PLEASE lol Link to comment Share on other sites More sharing options...
KHE Posted April 21, 2008 Report Share Posted April 21, 2008 Your car is slightly different than the RWD Broughams - the PASS key wires are on the 30 pin connector like you found. The resistor you soldered in must not be equal to the ignition key restance. What is your key resistance and what value of resistor did you solder in? Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
derbybug350 Posted April 21, 2008 Author Report Share Posted April 21, 2008 Luckily for me, I didnt solder in that resistor yet. The key pellets measure at 9.53 ohms and I got a 10 ohm resistor. The car wouldnt start or even turn over when I put the resistor in. Got that THEFT message until I hooked those wires back together without the resistor in it. I measured the resistance from the ignition side of those wires and it was at 0 until I inserted the key. Then it was right at 9.53 ohms. I wiggled the wires and banged on the colum and didnt see any change in the ohm reading. So I dont think the problem is in the column. Do you have any idea of where to check next or have a schematic for that wiring system? I still cant get the car started but I connected those wires back together and now I get the usual "service fuel system" message and it does turn over again now. Im stumped on where to go from here. I was really hoping that it was going to be the easy fix that you told me about but its still not working yet. Thanks for your help on this Link to comment Share on other sites More sharing options...
adallak Posted April 21, 2008 Report Share Posted April 21, 2008 Luckily for me, I didnt solder in that resistor yet. The key pellets measure at 9.53 ohms and I got a 10 ohm resistor. The car wouldnt start or even turn over when I put the resistor in. Got that THEFT message until I hooked those wires back together without the resistor in it. I measured the resistance from the ignition side of those wires and it was at 0 until I inserted the key. Then it was right at 9.53 ohms. I wiggled the wires and banged on the colum and didnt see any change in the ohm reading. So I dont think the problem is in the column. Do you have any idea of where to check next or have a schematic for that wiring system? I still cant get the car started but I connected those wires back together and now I get the usual "service fuel system" message and it does turn over again now. Im stumped on where to go from here. I was really hoping that it was going to be the easy fix that you told me about but its still not working yet. Thanks for your help on this Wiggling the wires down the column and banging on the column are not indicative because the weak part of the wires we have been talking about is right inside of the ignition cylinder... That part bends and rebinds every time you turn the ignition key... As I suggested before, use a spare key as a resistor to fool the system, if you think 10 Ohm and 9.53 can make a difference. I still believe you have a problem with wires inside of the ignition cylinder. If you had a chance to get there you would see the problematic area right away. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
derbybug350 Posted April 21, 2008 Author Report Share Posted April 21, 2008 I did use the spare key in place of the resistor and it still wouldnt turn over. I measured the resistance coming from the ignition side of the harness and it was right where it should be at 9.53 ohms but the "service fuel system" message still came up and the car still wouldnt start. HMMMMMMMM?!?!?!?!?! Link to comment Share on other sites More sharing options...
adallak Posted April 21, 2008 Report Share Posted April 21, 2008 I did use the spare key in place of the resistor and it still wouldnt turn over. I measured the resistance coming from the ignition side of the harness and it was right where it should be at 9.53 ohms but the "service fuel system" message still came up and the car still wouldnt start. HMMMMMMMM?!?!?!?!?! Well...al I can say is that your system probably differs from one on my car. Let's see if someone with your model year chimes in. Do not get frustrated! You'll fix it. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
winterset Posted April 21, 2008 Report Share Posted April 21, 2008 You might want to check the terminal block where you are plugging in the relay. There have been several issues reported lately that are related to corrosion on the underside of fuseboxes, & relay centers. This will also give the symptoms you mentioned. seems the connectors, wires turn green from salt etc. Link to comment Share on other sites More sharing options...
KHE Posted April 21, 2008 Report Share Posted April 21, 2008 If you are using a 10 ohm resistor, no wonder it won't start. The key pellet resistance is 9.53 K-ohms or 9530 ohms. You need to come up with a network of resistors that is close to 9530 ohms. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
adallak Posted April 21, 2008 Report Share Posted April 21, 2008 If you are using a 10 ohm resistor, no wonder it won't start. The key pellet resistance is 9.53 K-ohms or 9530 ohms. You need to come up with a network of resistors that is close to 9530 ohms. He probably used 10 k, besides he tried the spare key as a resistor as well... but yes, let me him recheck that resistor again. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
KHE Posted April 22, 2008 Report Share Posted April 22, 2008 If you are using a 10 ohm resistor, no wonder it won't start. The key pellet resistance is 9.53 K-ohms or 9530 ohms. You need to come up with a network of resistors that is close to 9530 ohms. He probably used 10 k, besides he tried the spare key as a resistor as well... but yes, let me him recheck that resistor again. 10K is not close enough to work - that is 470 ohms away from the target. I would use two 4.7K and one 100 ohm in series. That would be 9500 ohms and that should work. If the spare key connected in the system didn't work, it makes me wonder if he didn't have it on the wrong side (ignition side of the wiring vs. the vehicle side of the wiring). Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
derbybug350 Posted April 23, 2008 Author Report Share Posted April 23, 2008 I am using a 1 ohm resistor. My multi meter was set at 20k and the reading off the key was .953 so I asked the dudes at radio shack which resistors I needed and they said use a 1 ohm resistor. The pellet in the key is very small and therefore I needed a 1 ohm resistor. They come in different ohms and voltages and Im not that skilled in electronics yet so I went with what they told me. I did have the spare key on the vehicle side not the ignition side of the harness when I tested it and still got that message. I checked the relay center wiring and removed all four terminals to the fuel pump relay and cleaned them. There was hardly any corrosion on them but I noticed that one terminal was loose where the fuse plugs into it so I replaced that one. I also cleaned the wiring for the fuel pump fuse. There is a 50-60 wire connector just below the fuse block under the hood and I disconnected that as well and cleaned some corrosion from those terminals. The car now starts (so far) but Im not 100% certain that I cured the problem. I removed the relay while the car was running, and it stalled. I replaced the relay and started the car up and then removed the fuel pump fuse and again it stalled. Both times I got the "service fuel system" message in the read out. I think we're getting close here and I will keep you updated on the sucess or failure. Hopefully the former. Any other ideas are welcome if you think of any . If you can give me any more info as to how to determine the correct resistor, please do Link to comment Share on other sites More sharing options...
JimD Posted April 23, 2008 Report Share Posted April 23, 2008 I am using a 1 ohm resistor. My multi meter was set at 20k and the reading off the key was .953 so I asked the dudes at radio shack which resistors I needed and they said use a 1 ohm resistor. The pellet in the key is very small and therefore I needed a 1 ohm resistor. They come in different ohms and voltages and Im not that skilled in electronics yet so I went with what they told me. A pragmatist would say, "the car runs therefore problem solved!" Doing the math on your Ohmeter reading tells me your key resistance is 9,530 Ohms. That fits the scheme of a key blank #14; see this page http://www.thirdgen.org/vats_passkey_system I wont bore you with my opinion of the technical level of Radio Shack retail store employees. Hint: resistors are available in "different ohms" but not "different voltages". The first thing that comes into my head is your 1 Ohm resistor is really a 10K Ohm resistor and you got lucky. Jim Drive your car. Use your cell phone. CHOOSE ONE ! Link to comment Share on other sites More sharing options...
adallak Posted April 23, 2008 Report Share Posted April 23, 2008 I am using a 1 ohm resistor. My multi meter was set at 20k and the reading off the key was .953 so I asked the dudes at radio shack which resistors I needed and they said use a 1 ohm resistor. The pellet in the key is very small and therefore I needed a 1 ohm resistor. They come in different ohms and voltages and Im not that skilled in electronics yet so I went with what they told me. I did have the spare key on the vehicle side not the ignition side of the harness when I tested it and still got that message. I checked the relay center wiring and removed all four terminals to the fuel pump relay and cleaned them. There was hardly any corrosion on them but I noticed that one terminal was loose where the fuse plugs into it so I replaced that one. I also cleaned the wiring for the fuel pump fuse. There is a 50-60 wire connector just below the fuse block under the hood and I disconnected that as well and cleaned some corrosion from those terminals. The car now starts (so far) but Im not 100% certain that I cured the problem. I removed the relay while the car was running, and it stalled. I replaced the relay and started the car up and then removed the fuel pump fuse and again it stalled. Both times I got the "service fuel system" message in the read out. I think we're getting close here and I will keep you updated on the sucess or failure. Hopefully the former. Any other ideas are welcome if you think of any . If you can give me any more info as to how to determine the correct resistor, please do The resistance of your key cannot be 0.953 ohm... If the guys at RadioShack knew the difference between ohms and kohms they would not be working there! I believe someone (Logan??) had a list of resistances used by Cadillac (some 20 of them). Resistors come in different wattage not voltage. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
KHE Posted April 24, 2008 Report Share Posted April 24, 2008 I agree with JimD - leave it alone, drive it awhile to see if the problem is fixed. It sounds like the loose relay contact was the culprit. I'd leave the VATS connected and not bother with the resistors unless it starts acting up again. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
derbybug350 Posted April 24, 2008 Author Report Share Posted April 24, 2008 Alright guys Im an idiot. The resistor is a 10 ohm and it is 1/8 watt not volts. DUH!!! Sorry but Im not that skilled in the electronics field yet but working on it. The car is running and starting fine now and I will keep ya posted. Stay tuned. Sometimes it needs to crank more than what seems normal but other than that it is back to being a great car Link to comment Share on other sites More sharing options...
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