Possible Bad PCM
October 28th, 2018, 1:03 AM
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Possible Bad PCM
Hey folks, I recently rebuilt the engine of a 2 door 2000 Chevy Tracker, it's got the 2.0L J20, RWD A/T. You may have seen one or two of the posts I've made about some problems along the way, but this one's a bit of a mystery.
Essentially, sometimes the fuel injectors and spark plugs work, and sometimes they don't. To be more specific, to make sure they were firing I held the ignition packs/spark plugs in my hand and watched them spark. We listened to the injectors and heard them firing. Later when we tried again, no spark at all. The same thing also happened with the fuel injectors. We've been testing the circuits and they've been checking out so far, the injectors and spark plugs all seem to be receiving power.
On a more positive note, every now and then when we crank it, it tries to fire and start, which is a tad encouraging.
Also I have a pretty busy schedule and to keep a long story short I can only work on it when the stars align, and essentially when they did I couldn't get my hands on a scanner, so sorry but I have no error codes to share (yeah I know big help right?)
My first question is if there's a possibility it's an issue with the PCM? We've been trying to keep from pointing fingers at it, but it's legitimately starting to seem like it could be the problem. It's sat for like 3 years now and we have found evidence of rats in the thing, specifically the glove box, so god knows what they could've done.
Second would I have to replace it with the exact model number, 33921-65D31, or could I go with something from, for example, a 2001? I may get it tested and reprogrammed, but since there aren't any Suzuki dealerships in the U.S I'd have to hope that a Chevy dealership can do it.
Of course if anyone's got a suggestion as to what it may be something other than the PCM I'm more than open. At this point it seems like a man in China could sneeze make my problem 10x worse.
I'm also cross-posting this on other forums so sorry if you see it on another one too. Thanks!
Essentially, sometimes the fuel injectors and spark plugs work, and sometimes they don't. To be more specific, to make sure they were firing I held the ignition packs/spark plugs in my hand and watched them spark. We listened to the injectors and heard them firing. Later when we tried again, no spark at all. The same thing also happened with the fuel injectors. We've been testing the circuits and they've been checking out so far, the injectors and spark plugs all seem to be receiving power.
On a more positive note, every now and then when we crank it, it tries to fire and start, which is a tad encouraging.
Also I have a pretty busy schedule and to keep a long story short I can only work on it when the stars align, and essentially when they did I couldn't get my hands on a scanner, so sorry but I have no error codes to share (yeah I know big help right?)
My first question is if there's a possibility it's an issue with the PCM? We've been trying to keep from pointing fingers at it, but it's legitimately starting to seem like it could be the problem. It's sat for like 3 years now and we have found evidence of rats in the thing, specifically the glove box, so god knows what they could've done.
Second would I have to replace it with the exact model number, 33921-65D31, or could I go with something from, for example, a 2001? I may get it tested and reprogrammed, but since there aren't any Suzuki dealerships in the U.S I'd have to hope that a Chevy dealership can do it.
Of course if anyone's got a suggestion as to what it may be something other than the PCM I'm more than open. At this point it seems like a man in China could sneeze make my problem 10x worse.
I'm also cross-posting this on other forums so sorry if you see it on another one too. Thanks!
October 28th, 2018, 11:36 AM
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Maybe you have a loose or corroded PCM grounding wire. The worst mistake you can make is throwing another PCM at it without KNOWING that is your problem.You indicated that you found evidence of rats, and one thing they are good at is chewing through wire insulation. Say they have chewed through the harness, and damaged it so wires are now touching, and you install another PCM on top of that damage. Maybe the result will be that the replacement PCM just doesn't work, like this one now doesn't, or worse, shorted wires burn out the replacement unit so it acts like the one you have right now.
You could take out the PCM, open it up, and look for damage, or smell it to see if it smells burned.
I think you might do well to get a wiring diagram and a multimeter, and verify you have a good 0 ohm ground path as a start. Firing spark plugs and injectors takes a lot of amperage, and a flaky ground prevents that from occurring.
And yes, not having scan codes on a vehicle that may be telling you it has a bad crank or cam sensor makes it much harder to diagnose over the Internet.
You could take out the PCM, open it up, and look for damage, or smell it to see if it smells burned.
I think you might do well to get a wiring diagram and a multimeter, and verify you have a good 0 ohm ground path as a start. Firing spark plugs and injectors takes a lot of amperage, and a flaky ground prevents that from occurring.
And yes, not having scan codes on a vehicle that may be telling you it has a bad crank or cam sensor makes it much harder to diagnose over the Internet.
October 30th, 2018, 5:42 PM
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Maybe you have a loose or corroded PCM grounding wire. The worst mistake you can make is throwing another PCM at it without KNOWING that is your problem.You indicated that you found evidence of rats, and one thing they are good at is chewing through wire insulation. Say they have chewed through the harness, and damaged it so wires are now touching, and you install another PCM on top of that damage. Maybe the result will be that the replacement PCM just doesn't work, like this one now doesn't, or worse, shorted wires burn out the replacement unit so it acts like the one you have right now.
You could take out the PCM, open it up, and look for damage, or smell it to see if it smells burned.
I think you might do well to get a wiring diagram and a multimeter, and verify you have a good 0 ohm ground path as a start. Firing spark plugs and injectors takes a lot of amperage, and a flaky ground prevents that from occurring.
And yes, not having scan codes on a vehicle that may be telling you it has a bad crank or cam sensor makes it much harder to diagnose over the Internet.
You could take out the PCM, open it up, and look for damage, or smell it to see if it smells burned.
I think you might do well to get a wiring diagram and a multimeter, and verify you have a good 0 ohm ground path as a start. Firing spark plugs and injectors takes a lot of amperage, and a flaky ground prevents that from occurring.
And yes, not having scan codes on a vehicle that may be telling you it has a bad crank or cam sensor makes it much harder to diagnose over the Internet.
We haven't yet checked the grounds for the PCM connectors yet though, so there's still those to eliminate.
Thanks for the response!
October 30th, 2018, 9:24 PM
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What other parts have you replaced during your attempts to get the motor to start and run?
I see you mentioned a cam and crank sensor.
Without looking at a wiring diagram, I seem to recall that vehicle manufacturers will sometimes pair injection pulse with spark plug timing. One circuit accomplishing two things...
Was the vehicle running when you got it?
How many miles are on the odometer?
Is there a chance that someone tried jumping it off to your knowledge?
Have you put a fuel pressure gauge on the rail to verify you have 45-55 psi? Maybe you have a bad fuel pump, or a burned out fuse or relay.
I see you mentioned a cam and crank sensor.
Without looking at a wiring diagram, I seem to recall that vehicle manufacturers will sometimes pair injection pulse with spark plug timing. One circuit accomplishing two things...
Was the vehicle running when you got it?
How many miles are on the odometer?
Is there a chance that someone tried jumping it off to your knowledge?
Have you put a fuel pressure gauge on the rail to verify you have 45-55 psi? Maybe you have a bad fuel pump, or a burned out fuse or relay.
October 30th, 2018, 11:04 PM
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What other parts have you replaced during your attempts to get the motor to start and run?
I see you mentioned a cam and crank sensor.
Without looking at a wiring diagram, I seem to recall that vehicle manufacturers will sometimes pair injection pulse with spark plug timing. One circuit accomplishing two things...
Was the vehicle running when you got it?
How many miles are on the odometer?
Is there a chance that someone tried jumping it off to your knowledge?
Have you put a fuel pressure gauge on the rail to verify you have 45-55 psi? Maybe you have a bad fuel pump, or a burned out fuse or relay.
I see you mentioned a cam and crank sensor.
Without looking at a wiring diagram, I seem to recall that vehicle manufacturers will sometimes pair injection pulse with spark plug timing. One circuit accomplishing two things...
Was the vehicle running when you got it?
How many miles are on the odometer?
Is there a chance that someone tried jumping it off to your knowledge?
Have you put a fuel pressure gauge on the rail to verify you have 45-55 psi? Maybe you have a bad fuel pump, or a burned out fuse or relay.
It was running when we got it circa 2015, and was a daily driver and I learned how to drive in it. It broke down due to my mother driving it without oil for 6 miles early 2016, and it sat until I asked my parents if I could have it if I fixed it, and they said yes. We took out the engine and it sat without an engine outside in my grandparents' backyard from late 2016 to January 2018, when we put the engine back in. There are currently 219,394 miles on it.
When we rebuilt the engine from 2016-2018, I put a new crankshaft and crankshaft bearings, new .04" oversized piston heads/rings, had to bore the block, rebore the rod journals (except one, that had to be replaced), a new camshaft sensor (the old one was broken taking the engine out), new gaskets in the upper engine, and new timing chains with a new lower chain tensioner.
After getting it all put together, put back in and hooked up, we tried to start it but it wouldn't start. It'd crank, but no spark. A local mechanic figured it was probably the crank sensor, so we dropped the transmission and replaced it, then put it all back together again and tried to start it with no spark again. Around that time I found a factory service manual on the engine from Suzuki, so we ditched the Hayne's guide. According to the FSM, the crank sensor doesn't have anything to do with the ignition/injection timing, it's all through the camshaft sensor. When we put a multimeter on it to test the circuit and turned it over, to our surprise a cylinder fired. Since then we've had an issue with the spark plugs firing sometimes and not firing others. It also seems the same is happening with the fuel injectors.
The fuel injectors and spark plugs are on separate circuits leading back to the PCM, with the camshaft sensor on the spark plug/ignition coil circuit. The fuel rail is being pressurized, while we don't know the exact PSI, it's pressurized enough to know the fuel pump is doing its job. And nobody has tried jumping it, but we have had to charge it multiple times since cranking it drained the battery, and every time it was charged I was aware it was being charged.
October 31st, 2018, 12:52 AM
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Thank you for the update.
With all of the work you have done, maybe it is time to step back and verify some things.
I don't know what your level of expertise is, so these are things that you can check off as a list.
You can never assume that someone else connected anything correctly. Personally, I commend you for getting this far on your project.
I would go around the engine bay, and make sure that every single ground wire is making a solid contact. The car sat in the weather for an extended period, and it is 18 years old. I just chased down a bad ground on my current truck, because I was having charging problems and replacement alternators didn't help. That problem took me eleven days to find and fix.
In your case, everything was running, which means all the wires were connected properly. With the engine being removed and replaced, there is a chance that a wire was left unconnected, or maybe got broken with the work.
With 219,+ thousand miles on the unit, I would definitely want to lay my hands on a fuel pressure tester. You can get a fuel pressure testing kit as a loan-a-tool from AutoZone or another store that offers it which will allow you to make sure you have enough pressure behind the injectors to provide an adequate fuel delivery to a freshly rebuilt engine, one that offers higher resistance to an incoming charge, due to its higher compression. 20 psi may tell you that the filter is clogged, even if that is still enough to pressurize the rail. Your FSM will tell you what your minimums need to be. If it is flaky, it is a fail-point waiting to strand you somewhere, and maybe it already has..
I don't normally recommend this, but have you tried using any short bursts of anything flammable into the intake stream while cranking the motor? If the car will run on either, it eliminates bad compression and a no-spark condition.
Another thing that may have gone flaky over a long dormancy is the ignition switch. When I used to drive a Mazda truck, and even though it never happened to me, there were many owners of the trucks who found partial engagement of the switch would cause the truck to crank, but not start, unless the key was forced all the way to the stop. Most people only turn a key to a point where they hear the starter engage, and no further. Maybe you could try cranking the engine in neutral as an alternative to cranking it in park.
One other thing comes to mind, from a personal experience. I had a Nissan Maxima with a V-6, and even though I thought I was a mechanic, I had to tow the car to a shop to get the ones with the experience to fix it. Turns out the coolant temperature sensor was corroded where the wire connected to the switch, creating an artificially high resistance. What that did was fool the computer into feeding too much fuel once the engine started to warm up, in effect, drowning the cylinders with too much fuel.
It probably isn't the same in your case, but I offer the story to show you the headaches one bad wire can cause.
With all of the work you have done, maybe it is time to step back and verify some things.
I don't know what your level of expertise is, so these are things that you can check off as a list.
You can never assume that someone else connected anything correctly. Personally, I commend you for getting this far on your project.
I would go around the engine bay, and make sure that every single ground wire is making a solid contact. The car sat in the weather for an extended period, and it is 18 years old. I just chased down a bad ground on my current truck, because I was having charging problems and replacement alternators didn't help. That problem took me eleven days to find and fix.
In your case, everything was running, which means all the wires were connected properly. With the engine being removed and replaced, there is a chance that a wire was left unconnected, or maybe got broken with the work.
With 219,+ thousand miles on the unit, I would definitely want to lay my hands on a fuel pressure tester. You can get a fuel pressure testing kit as a loan-a-tool from AutoZone or another store that offers it which will allow you to make sure you have enough pressure behind the injectors to provide an adequate fuel delivery to a freshly rebuilt engine, one that offers higher resistance to an incoming charge, due to its higher compression. 20 psi may tell you that the filter is clogged, even if that is still enough to pressurize the rail. Your FSM will tell you what your minimums need to be. If it is flaky, it is a fail-point waiting to strand you somewhere, and maybe it already has..
I don't normally recommend this, but have you tried using any short bursts of anything flammable into the intake stream while cranking the motor? If the car will run on either, it eliminates bad compression and a no-spark condition.
Another thing that may have gone flaky over a long dormancy is the ignition switch. When I used to drive a Mazda truck, and even though it never happened to me, there were many owners of the trucks who found partial engagement of the switch would cause the truck to crank, but not start, unless the key was forced all the way to the stop. Most people only turn a key to a point where they hear the starter engage, and no further. Maybe you could try cranking the engine in neutral as an alternative to cranking it in park.
One other thing comes to mind, from a personal experience. I had a Nissan Maxima with a V-6, and even though I thought I was a mechanic, I had to tow the car to a shop to get the ones with the experience to fix it. Turns out the coolant temperature sensor was corroded where the wire connected to the switch, creating an artificially high resistance. What that did was fool the computer into feeding too much fuel once the engine started to warm up, in effect, drowning the cylinders with too much fuel.
It probably isn't the same in your case, but I offer the story to show you the headaches one bad wire can cause.
Last edited by Kazoocruiser; October 31st, 2018 at 1:26 AM.
November 2nd, 2018, 5:43 AM
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Hey so sorry for taking so long. I remember getting the notification but I've had so much homework it just slipped through the cracks. My level of expertise is very minimal, everything I know about mechanics is actually knowledge I learned from doing this. This isn't to say I went at this without knowing what I was doing alone; my grandfather who was a motorcycle mechanic for several years, went to school for electrical engineering, and was a mechanical engineer for Boeing and Koch for a long time has been helping me the entire way. He's essentially been the brains of the operation.
Everything we had to unplug to uninstall and reinstall the engine has been plugged in, but we haven't checked any other wires. There could very possibly be a damaged wire that we haven't thought to check.
As for something flammable, would this be something along the lines of starter fluid? We haven't tried anything like that. It certainly sounds worth looking into if it can get rid of a no spark condition.
Next time we try to start it I'll shift it into neutral and turn the key further. That's an interesting point to bring up; maybe we should explore possibilities other than the engine.
And dang that really sucks about your Maxima, that really does sound like a headache. I'll have to look for a better wiring diagram so I can see where everything goes and intersects so I can actually track down the wires and inspect them.
Thanks so much for all the advice, I really do appreciate it! I'll update you next time I get a chance to work on it. My grandfather's going to Mexico for a week sometime soon though so it may be a while before I do. Thanks again!
Everything we had to unplug to uninstall and reinstall the engine has been plugged in, but we haven't checked any other wires. There could very possibly be a damaged wire that we haven't thought to check.
As for something flammable, would this be something along the lines of starter fluid? We haven't tried anything like that. It certainly sounds worth looking into if it can get rid of a no spark condition.
Next time we try to start it I'll shift it into neutral and turn the key further. That's an interesting point to bring up; maybe we should explore possibilities other than the engine.
And dang that really sucks about your Maxima, that really does sound like a headache. I'll have to look for a better wiring diagram so I can see where everything goes and intersects so I can actually track down the wires and inspect them.
Thanks so much for all the advice, I really do appreciate it! I'll update you next time I get a chance to work on it. My grandfather's going to Mexico for a week sometime soon though so it may be a while before I do. Thanks again!
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November 4th, 2018, 10:44 PM
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Hi, I had some time to think some more about your non-starting condition.
When you tested the sensors, where did you take your readings? Were you getting a 5+vdc signal?
Have you used a logic probe to test for current?
When you tested the sensors, where did you take your readings? Were you getting a 5+vdc signal?
Have you used a logic probe to test for current?
November 14th, 2018, 1:26 AM
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Hey Kazoocruiser I'm so sorry for this late reply, I've been meaning to do so for a while but schoolwork and errands have got the best of me lately. When we tested the sensors, we were taking them from the connector of the PCM, as for the signal I can't remember specifically. I haven't had a chance to work on it in a while. However, we haven't used a logic probe. I watched the video and it was very informative, and I certainly am considering getting one.
Unfortunately, it's getting a lot colder, and in fact it recently snowed where I'm at, and since we don't have a shop to work on it in, we have to work outside meaning it is becoming less and less of an option. This Thursday I'm loading it on a trailer and bringing it to a mechanic for diagnostics, and potentially fix it. I really wanted to stay in the fight to the end, and I still might if having the mechanic fix it will cost too much, but my time to get it running is wearing thin. If I can pay a mechanic to get it done quick, that's the road I'm headed down.
Regardless, thank you so much for your help and advice! I appreciate it a ton and if I still end up being the one to fix it I'll be more than happy to put it to use.
Unfortunately, it's getting a lot colder, and in fact it recently snowed where I'm at, and since we don't have a shop to work on it in, we have to work outside meaning it is becoming less and less of an option. This Thursday I'm loading it on a trailer and bringing it to a mechanic for diagnostics, and potentially fix it. I really wanted to stay in the fight to the end, and I still might if having the mechanic fix it will cost too much, but my time to get it running is wearing thin. If I can pay a mechanic to get it done quick, that's the road I'm headed down.
Regardless, thank you so much for your help and advice! I appreciate it a ton and if I still end up being the one to fix it I'll be more than happy to put it to use.