gzibell Posted July 28, 2014 Report Share Posted July 28, 2014 Hey Everyone, I am looking for some advice and wisdom. Been having some very odd issues with my grand prix. A while back I posted a questions here http://www.w-body.com/showthread.php/78376-98-Grand-Prix-GTP-Tranny-Issues. Thought there might be a TCC solenoid issue. Ended up parking the car for the remained of the winter in my garage. Sat for maybe 4 months. This spring, decided to fire it up and see if the tranny was still having issue since the temperature was like 100 degrees warmer, (ND, -30 to 70). Tried to fire it up and had no fuel pump wine cause it was not running and would not start. Messed around with it a bit, wiggled some wires and such nothing much and it fired up and I drove it around a bit and the tranny acted normal. Parked it along side the garage and it sat for maybe 2 months. Now it will not start at all. Fuel pump will not engage at all, so I shoved a jumper wire in the fuel pump relay to see if it would work. Fired right up. Don't have a gauge but tons of pressure in the fuel rail, hit the little valve and poof gas everywhere. Only did that once. Cranked and Cranked with the jumper in place nothing. Next step, maybe something got it and chewed on some wires and I am not getting spark, out comes the starting fluid. Once shot and a second on the key and vroom, for a second. So I am obviously getting spark but no gas. Messed around with it for a while, tested voltage on injectors, inspected, etc. etc. Nothing. I decided to hook up my scan tool to see if I could get anything and it would not connect to the ECU. Tried it on my wife's card to verify the scan tool still worked and it connected and read codes as it should. Tried again and again. Took the ECU out of the car disassembled and inspected for corrosion, burnt marks, magic smoke smell and all seemed well. Reinstalled and still nothing. I am at a loss. Everything seems to be fine. But I am considering the ECU as the culprit for all of my issues now, electronically controlled TCC and shit points giving trouble initially, but ran fine, now nothing. Only common component that I can think of that has anything to do with shifting and fuel is the ECU. Oh and I did crank on it for a good while and pulled a plug and they were bone dry. I have been researching and saw some things like, make sure you have a good ground clean it up, but really would it crank over with a bad ground but prevent the ECU from doing what it does. The ECU is not externally grounded to anything so must be a main ground off the battery? Also read that you cannot just grand an ECU out of a same year make and model OBD2 as it has to be programmed for the VIN, is this true? Was thinking about seeing if the local junk yard had one. Anyone ran into issues like this or have any suggestions on where to look/what to look for. Don't want my yard to turn into a junk yard so I either have to getting it running to drive or so I can part with it and let someone else enjoy it for a while. Thanks is advance, any assistance is greatly appreciated. Quote Link to comment Share on other sites More sharing options...
Schurkey Posted July 28, 2014 Report Share Posted July 28, 2014 Battery fully charged? All the fuses good? ECM is actually powered? Quote Link to comment Share on other sites More sharing options...
gzibell Posted July 28, 2014 Author Report Share Posted July 28, 2014 Battery fully charged? All the fuses good? ECM is actually powered? Had the charger on the battery. Cranked over like a champ. Check fuses related to fuel pump, ecu, and other related. Am I missing an important one? No idea if the ecm is actually powered. Is there a way to tell? Scan tool could not connect so I was assuming it was not. That is actually why I started checking fuses. Quote Link to comment Share on other sites More sharing options...
rich_e777 Posted July 28, 2014 Report Share Posted July 28, 2014 Get yourself a test probe light and start checking for power. You mentioned messing about with a few wires and then your issue went away temporarily, that would seem like a damaged wire or bad connection. Not sure about GTP ECU interchangeability, but you can get yourself some ALDL cables and download tunerpro RT to see what the ECU is doing on a laptop. Quote Link to comment Share on other sites More sharing options...
gzibell Posted July 28, 2014 Author Report Share Posted July 28, 2014 Get yourself a test probe light and start checking for power. You mentioned messing about with a few wires and then your issue went away temporarily, that would seem like a damaged wire or bad connection. Not sure about GTP ECU interchangeability, but you can get yourself some ALDL cables and download tunerpro RT to see what the ECU is doing on a laptop. Grabbed a test light quick and hit both sides of the ecm fuses with the key on. Got power on both. Tests a handful of wires going in to the ecm and had power there to. As a note, when I wiggled wires before it was at the fuel pump as I assumed that was dead. Nothing under the hood. Like I said in opening post, jumping fuel pump relay fires the pump right up. Quote Link to comment Share on other sites More sharing options...
Nas Escobar Posted July 28, 2014 Report Share Posted July 28, 2014 Get yourself a test probe light and start checking for power. You mentioned messing about with a few wires and then your issue went away temporarily, that would seem like a damaged wire or bad connection. Not sure about GTP ECU interchangeability, but you can get yourself some ALDL cables and download tunerpro RT to see what the ECU is doing on a laptop. His car is a 98. He would need something for OBD2. ALDL is for OBD1 and I believe it's GM specific. Quote Link to comment Share on other sites More sharing options...
gzibell Posted July 28, 2014 Author Report Share Posted July 28, 2014 His car is a 98. He would need something for OBD2. ALDL is for OBD1 and I believe it's GM specific. I did some researching on that a bit after the post and found the same answer. Used to have one for this car but it has gone away to somewhere. I am not sure that would help much as I cannot connect to the ecu with an obd2 scan tool. I am researching to find a pinout for the ecm to see make sure there is power there for sure. After I thought about it, some of the lines to the ECU may be energized even if the ECU is not getting power. I am also going to try a noid light or whatever they are called to make sure the fuel injectors really are not firing. Quote Link to comment Share on other sites More sharing options...
Nas Escobar Posted July 28, 2014 Report Share Posted July 28, 2014 I did some researching on that a bit after the post and found the same answer. Used to have one for this car but it has gone away to somewhere. I am not sure that would help much as I cannot connect to the ecu with an obd2 scan tool. I am researching to find a pinout for the ecm to see make sure there is power there for sure. After I thought about it, some of the lines to the ECU may be energized even if the ECU is not getting power. I am also going to try a noid light or whatever they are called to make sure the fuel injectors really are not firing. Is there a specific reason you can't connect with a scan tool? The scan tool would be the most definite way since no data means a fault within the ECU. Can you get a loaner? Quote Link to comment Share on other sites More sharing options...
gzibell Posted July 28, 2014 Author Report Share Posted July 28, 2014 Is there a specific reason you can't connect with a scan tool? The scan tool would be the most definite way since no data means a fault within the ECU. Can you get a loaner? Oh, I have a scan tool. It will not connect to the ecm... Tried the scan tool on other cars to verify it works but it will not connect to the ecm on the grand prix. There has to be something obvious that is wrong somewhere. Can an ecm going out cause strange shifting behavior? I am trying to relate these together if possible. Related or not, scan tool will not connect to car, as far as I can tell, have spark but no fuel injector pulse. Which makes sense as the fuel injectors are driven by the ecm. Right? Quote Link to comment Share on other sites More sharing options...
Nas Escobar Posted July 28, 2014 Report Share Posted July 28, 2014 At the least the connector may be shorted or bad but I think it may be the ECU itself. A bad ECU can cause many strange and erratic behaviors. The most common is the car not starting because the ECU doesn't engage the fuel pump to prime nor deliver fuel. It can also cause the coils not to fire. So yes trans issues can be related since its an electronic trans. The ECU tells it how and when to shift. If you ever noticed the trans will stay in gear longer when floored than when cruising. That's the ECU dictating. What I would do is verify the ECU is bad and go from there. If you get the same issues with s verified good ECU then the next place to look is connections and wiring because you already verified a working pump. Quote Link to comment Share on other sites More sharing options...
gzibell Posted July 29, 2014 Author Report Share Posted July 29, 2014 At the least the connector may be shorted or bad but I think it may be the ECU itself. A bad ECU can cause many strange and erratic behaviors. The most common is the car not starting because the ECU doesn't engage the fuel pump to prime nor deliver fuel. It can also cause the coils not to fire. So yes trans issues can be related since its an electronic trans. The ECU tells it how and when to shift. If you ever noticed the trans will stay in gear longer when floored than when cruising. That's the ECU dictating. What I would do is verify the ECU is bad and go from there. If you get the same issues with s verified good ECU then the next place to look is connections and wiring because you already verified a working pump. I got a pinout diagram from another website. Checked a bunch of the connections and it seems there is power where there needs to be. I was able to get the oe part number off it. See if the local junk yard has one on hand. Give that a try and see if anything new happens since they are only 25 bucks. Local gm dealer said as long as the number is the same it should work. Hopefully I can at least communicate with the new ecm it it thows a code heck, I'd be happy with a back fire at this point. Quote Link to comment Share on other sites More sharing options...
gzibell Posted August 1, 2014 Author Report Share Posted August 1, 2014 Ok, So no go on the new ecm...nothing changed when I installed. I check every fuse and relay and all are good. There must be a broken or worn wire somewhere. Any suggestions on where I should start looking? Something is preventing the ecm from doing what it is supposed to. I wonder if over time one of the bundles of wires shifting slightly has worn away the insulation and is casing shorts and such coming off the ecm harness. If that is happened, that might explain some of the issues with the odd tranny behavior. After sitting for a bit I wonder if a bit more corrosion happened which finally broke the connection completely. Is there a good place to start or should I start on one end and work my way to the other? Quote Link to comment Share on other sites More sharing options...
Imp558 Posted August 1, 2014 Report Share Posted August 1, 2014 If jumping the relay makes it run than you likely have corrosion along the wire that runs from the relay to the pump, it sounds funny but that little bit of added resistance from the relay was the last straw for mine and it wouldn't run. If jumping the relay isn't reliably making the pump run you need to determine if there's a signal from the PCM to the relay, rig a lightbulb between where the FP relay plugs in to 85 and 86 and turn the key to run. If the light lights up for a few seconds it means the PCM is enabling the FP Relay via a green wire with white tracer, and that the ground to the relay coil is good. Pins 87 and 30 are the switch, you should find system voltage on one, and the other goes to the pump. Quote Link to comment Share on other sites More sharing options...
gzibell Posted August 1, 2014 Author Report Share Posted August 1, 2014 If jumping the relay makes it run than you likely have corrosion along the wire that runs from the relay to the pump, it sounds funny but that little bit of added resistance from the relay was the last straw for mine and it wouldn't run.If jumping the relay isn't reliably making the pump run you need to determine if there's a signal from the PCM to the relay, rig a lightbulb between where the FP relay plugs in to 85 and 86 and turn the key to run. If the light lights up for a few seconds it means the PCM is enabling the FP Relay via a green wire with white tracer, and that the ground to the relay coil is good. Pins 87 and 30 are the switch, you should find system voltage on one, and the other goes to the pump. I will give the light bulb trick a try but I think I already know what the answer will be. Correct me if I am wrong but if the PCM was sending the signal to initiate the pump but there was corrosion or something like that, wouldn't jumping the relay act the same way? Also, it appears that the ECM is also not telling the injectors to fire either. As I jumped the fuel pump relay, attempted to start, and the plugs remained dry. Jumping the relay makes the pump run like crazy but it will still not fire at all so I am pretty sure I am not getting fuel injectors either which it why I thought the ecm was bad. I am not really sure how the ecms work but if you remove the fuel pump relay and jump it on a car that currently runs will it start? When you had the bad wire did yours do anything at all, did jumping the relay allow you to start the car? Quote Link to comment Share on other sites More sharing options...
Schurkey Posted August 1, 2014 Report Share Posted August 1, 2014 Key on, engine off: Does the SES/Check Engine light illuminate? Quote Link to comment Share on other sites More sharing options...
gzibell Posted August 1, 2014 Author Report Share Posted August 1, 2014 Key on, engine off: Does the SES/Check Engine light illuminate? It does not. Quote Link to comment Share on other sites More sharing options...
gzibell Posted August 1, 2014 Author Report Share Posted August 1, 2014 (edited) Also just tested all fuel pump relay circuits with a light as recommended. Connected to one at a time, turned key on, no light, key off, next connection. All showed nothing except one of course which is constant 12. What would prevent the ecm from engaging the fuel pump? It is not even trying. Edit,, my scan tool can not see the ecm either. It it's like the ecm is not powering up. Edited August 1, 2014 by gzibell Quote Link to comment Share on other sites More sharing options...
Schurkey Posted August 1, 2014 Report Share Posted August 1, 2014 If the SES/Check Engine light bulb is burned-out, the scan tool may not be able to connect to the ECM. Might be worth you time to BUY A SERVICE MANUAL for this vehicle, and to assure that the SES/Check Engine circuit (including the bulb) is in usable condition. Quote Link to comment Share on other sites More sharing options...
gzibell Posted August 1, 2014 Author Report Share Posted August 1, 2014 If the SES/Check Engine light bulb is burned-out, the scan tool may not be able to connect to the ECM. Might be worth you time to BUY A SERVICE MANUAL for this vehicle, and to assure that the SES/Check Engine circuit (including the bulb) is in usable condition. Picked up a Service Manual over lunch to see if it has any clues in it. I will check that circuit to see if it is in usable condition but find a hard time believing that GM would wire/program a car that way. Seems a bit silly to me but I have see stranger things. Quote Link to comment Share on other sites More sharing options...
gzibell Posted August 2, 2014 Author Report Share Posted August 2, 2014 SOLVED!!! Found a orange wire on the ecm that was supposed to be 12 volts constant. It was dead. Ran a new fused line, fired right up. Amazing that a car with 275k can still smoke tires and lay black for a loooong time. Quote Link to comment Share on other sites More sharing options...
Schurkey Posted August 2, 2014 Report Share Posted August 2, 2014 I will check that circuit to see if it is in usable condition but find a hard time believing that GM would wire/program a car that way. Seems a bit silly to me but I have see stranger things. Done deliberately to prevent folks (used-car lots and other unethical people) from removing the Check Engine/SES light bulb and pretending that there was nothing wrong. When the scan tool won't provide data, that's the first thing to check. Congrats on finding the dead wire. Does the Check Engine/SES light come on during key on/engine off operation? Quote Link to comment Share on other sites More sharing options...
gzibell Posted August 2, 2014 Author Report Share Posted August 2, 2014 Yeah. Ses light flashes on key on. Goes out right away though. Quote Link to comment Share on other sites More sharing options...
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