96 2.4 ls cavalier manual sudden electrical issues abs ECM
Ok so my scan tool only had been showing I needed a catalytic converter, so
today I changed a tail lamp and my abs light came on before i even moved the
car. I plugged into the data connector and now it shows 32 fault codes not
related to the abs. Innova but it read the live data with a couple of issues doing
it showing nearly all of the failed devices working right but the intake
temperature sensor and the cat issue. It was in closed loop and still running
fine but I can’t communicate with the abs module. Was some water intrusion
inside the cabin but it’s been dry for months and not driven. My question is
what would the connection be between the abs and the ECM all showing
faults at the same time the abs light came on? It showed no communication
with the cam, crank sensor and the temperature sensor for the fans and a
number of other faults but runs and works fine. Although my battery died and I
had to recharge it after sitting for two years. I didn’t short anything and did a
visual inspection finding nothing but i haven’t dug in as deep as to checking
the ECM out.
Sounds like you have corrosion issues. So did out your wiring diagrams and component locator and start by cleaning the grounds as they are affected first at attachment areas, pay close attention to all sensor grounds, I can't remember just how many loose, corroded or broken grounds I have found over the years especially on GM products. Remember that after any wiring repairs or loss of main power you need to run the drivetime protocol before any real testing can be done.
I was forced to retire ten years ago I don’t have access to the wiring diagrams anymore, was fine three days ago but it’s a convertible that had a water leak leaving a small puddle on my driver side front floor pan. Is there any modules on the floor around that area? I looked at the wiring I could and didn’t find much corrosion except for two unrelated fuses to the lighting. I don’t live in the salt belt and I’m not finding any corroded wiring anywhere but I have yet to check underneath the vehicle
I've had the same problem getting information after retiring but have found my local library to be a great help for copies as well as EBay for manuals. You will only find a few grounds underneath, fuel pump, body to engine and maybe an engine to cradle ground. A lot of grounds that cause issues are up under the dash, on both sides where the dash is bolted to the body. There are also a few grounds on the main dash mounting rail that goes across the under the dash, under the driver seat will be some grounds for seat controls, the passenger side will have more grounds and modules. HTH
Ya our libraries don’t have much of anything for repair manuals and I don’t have a computer anymore, I can’t find anything online and don’t have the ability to remove the dash especially not knowing what I’m looking for. I can’t afford another car because my health is so poor and no one in Multnomah County has any experience or knowledge as far as master techs haven’t been able to find one in 12 years.
If your library is the pits, like mine is in Polk county, then you're stuck with either a professional (not worth it today) or EBay for a shop manual, a good one can be expensive even through EBay, however if your health is that bad you can't even get under the dash to even get to the issues, then forget master Techs, anymore that is just a name, doesn't mean anything like it did in my days and probably yours. At 70 years I have found that I can no longer get up under a dash anymore either but still can do most normal stuff. On some of the stuff I just can't do, I have found some very good backyarders that know their stuff as most all of them had been in dealerships and moved on either with owning their own shops or went into public transport or safety/emergency services. So they still have access to Alldata. You need to find an old school tech in your area that knows his stuff, might even be a word-of-mouth type of guy. Quiet and behind the scenes. Good Luck
site error.
Ya i just got ripped off by someone that looked legit for 700$ the state I live good technicians are impossible to find, i don’t think it’s any of the positive connections I’ve checked just about all of them, looks like there might be a ground by the driver rear engine compartment hidden somewhere that at least connects to the abs, guessing that must be where the ECM or other devices ground out at being as it all failed at exactly the same time. I do have a spare abs module on my z24 that got totaled but I don’t think it’s that unless somehow it’s screwing with the can network but i found a diagram that shows it being separate from the ECM on the DLC is that right? I don’t think in 96 Chevy had the abs linked to the ecm and the diagram shows it’s not but I can’t remember. I’m not sure if the data line to the ECM is linked to any other modules unlike new models, there is a video on YouTube on how to check the network using a multimeter that’s supposed to work on any obd2. Had no problems with my scan tool before but now it doesn’t want to communicate with everything. The abs light went off briefly but as soon as i pushed in the clutch it came back on and stayed on. I don’t know what it is with these cavaliers but even my z24 did something similar with the airbag light and lighting issues with the BCM.
Yes even in 96 the ECM and the BCM communicated with each other through the canbus circuits. The ABS is separate but uses the communication pathway to turn on warning light for that system. I just remembered a warning that was sent out years ago about BCM connectors and groundlug under the passenger seat. If you can find it then make sure the BCM's connectors are clean and free of corrosion and the ground wire that is attached to the seat rail mounting rib is also clean and free of corrosion, there was also a picture showing where moisture had got into the BCM and it had corrosion inside on the circuit board. ECM's back then had more than just one ground.
Ah ok now things are making sense if that indeed is where the bcm is being a convertible and a rare ls I saw a comment saying it was above the ECM but i think it is under the seat because when I got the car the window passenger side was stuck down and water flooded the passenger side all the way to the back rusting the seat so bad the release lever won’t let the seat move up from the wire breaking to the other release latch underneath. That entire area was under water i cleaned up what i could but i have no idea how I’m going to get the seat out with it stuck all the way back I may have to cut the back feet to get it out unless i can reach the release latch on the other side.i bet corrosion finally made it through messing with the canbus line.the rear view mirror lights don’t work either the passenger side was really bad because the mechanic left it out in the rain he was salty because he couldn’t figure out the misfire caused by someone attaching a ground strap to the coil cover underneath grounding the secondary windings out on one coil.900$ just for him to throw a fuel regulator on it that it didn’t need he didn’t even change or look at the plugs or oil. I swear if it isn’t in a book or on a computer mechanics these days have no idea what to do.i learned without computers by books and cds and keeping in touch with technicians until 2015 when things started getting really complicated and my scan tool and two channel oscilloscope wasn’t enough. Damn seat i knew in the back of my mind eventually i was going to have to pull it out i just had a gut feeling.
You got that right about the code thing. I've got a 2013 Silverado with the 5.3 and just before covid it would make a noise that sounded like lifters, as it was under a dealer warranty, I took it into the dealership to get it checked over, even had a video with sound showing what was happening, they had 5 days and couldn't find anything because it wasn't throwing any codes, I asked them if they drove it, and they said no, I asked why not, they said cause it was showing codes and it wasn't making any sound they didn't feel it was necessary. I said I'll be right there and show them, I go the service manager, and we went for a little drive, before we went 1/4 mile on a very slight hill right near the dealer it started making the sound, he said shut it off, so I did, and he said okay now I hear the sounds, I went back home and called than 2 days later. They couldn't find anything wrong with it cause the computer showed nothing wrong. I asked if they had any old guys there that worked on the older cars and he said only one, I said let him drive around and see what he finds, next day they called me back and had found that the starter Bendix was broken and would allow the starter drive to hit the ring gear every time the rig was even in a slight downhill surface. They replaced the starter assembly and no more sound. So even today seat of the pants tests are still valid, you just need some older mechanic sometimes.
Sorry that was suppose to be uphill surface for the starter drive.
Eyes ears nose, the three most important things to use before touching anything. Got the seat working again can’t tell if there is a computer or any ground points there but I see a lot of wiring going by that area and a plastic vent but I can’t get one straight answer what is underneath so i guess the seat is coming out and I’ll lift the carpet and see. Between 97-99 ppl say the bcm is either side above the kicker panels but mostly on the passenger side. PCM ECM are supposed to be the same part in one in front of the passenger wheel under a ton of plastic. It’s definitely not on the driver side but if it’s like the other models the dash has to come out one guy saying no just remove the plastic and I can reach the plug. My vin says it’s one of ten made so I don’t want to junk my car over this but I’m afraid if I drive it wherever the corrosion is could make things much worse. The fuses inside were corroded so moisture was really bad at one point might have to test the fuse block from behind. The dash is no joke to get out on these and may be the only answer at some point once i have a diagram of the engine harness and the interior harness. I know one older guy that might be able to do the work but i would have to talk him out of using alldata to get the diagrams and hunt down the problem areas and look for corrosion. If he is still in business and has a better scan tool that can look at all the live data but he generally doesn’t work with older cars with problems like this. He is about 30 minutes away and may be my last resort if i can do the diagnosing for him or his son. Only one car in my life ever stumped me like this a stratus someone switched the speed sensor wires around backwards on purpose causing a no start, the mechanic who diagnosed it retired years ago though when timberline dodge shut down. The same thing happened with a stuck window on my 98 z24 only different issues but a huge puddle on the passenger side in the same exact way.
Not sure what I just did but now I’m down to 17 faults not including the abs all with a o2 heater fault egr fault and evap fault and catalytic converter fault, I’m going to be so salty if this is just a issue with my downstream o2.
Airbag module was underneath the seat unharmed by the water, bcm is under the dash somewhere on passenger side i think near the windshield firewall area. I think the o2 shorted something when it blew causing the other issues or the interior fuse block has a rotten fuse connector that is where all the corrosion is at. A off fuse labeled elrs has a really bad connector I need a wiring diagram and a decent scan tool to get any further but I’m fairly sure one or more damaged modules from a heated o2 shorting out. Doesn’t even look like i can pull the abs module to test for power and ground without pulling the entire dashboard out. Pretty sure the ecu or ECM is damaged no shorted fuses 17 codes all related to the same circuit. Have to complete a drive cycle probably to get the abs codes. Egr, downstream o2, evap codes. I’ll test for power later when i recover see if i unplug the o2 if i get anything back it’s the most likely source of a short. No clue how it effected the abs module unless there is some hidden fuses I don’t know about. At least i can drive it the damage is already done.
Site issues. answers not posting.
So my scan tool is definitely having issues live data isn’t that great map pressure shows 30 engine off and 8 inches engine on, the rest of the live data shows slow responses but the pending codes it’s showing doesn’t seem to coincide with the live data. Need the right scan tool and hopefully a drive cycle will give me more accurate information my scanner is definitely garbage for this. Once i know exactly what isn’t working right a attempt at tracing it on on a wiring diagram can be made but from my experience with Chevy when a heated o2 shorts to ground it takes out a entire chain of circuits. My scanner is supposed to support more than 17 pids but i can’t get it to update like it’s supposed to so it will let me used the enhanced version. I swear there must be hidden fuses somewhere because neither fuse block has more than one fuse for the pcm and the microprocessor on the gauge cluster.
Good story about your truck, Gene! That proves how much the automotive service industry has devolved in, probably, the last 20 or so years! These so called "techs" today are clueless if the vehicle can't tell them what's wrong with it or if it's not staring them in the face! Very disappointing!! Thanks for sharing!! Jim
So here is how bad a innova scanner is, mind you first it’s showed no pcm activity but the car ran fine, I then noticed this and that engine off 30 inches of vacuum engine on 8 inches of vacuum with activity. Showing it’s running rich and lean no com srs and abs. Since the abs light came on everything else went Christine but the warning lights for everything else stayed off. Found the interior fuse for the pcm and abs which is good but I have yet to see if any power is on the load side of the fuse block. I’m pretty sure I can figure this out without an expensive scanner because of how old it is but I need a complete wiring diagram inside and out for the pcm and ECM and abs. I can’t even find one that I can buy online because of the cars age and because it’s a convertible manual. My next step is checking for power first at the fuse blocks then the o2s then the evap valves and the egr. If i unplug the load circuit on each one and voltage comes back it may tell me something but the fact that the abs module is doing nothing I’m thinking somewhere from the interior fuse block to the abs and pcm i have power failure as a com issue would make itself very apparent with the gauges and the motor wouldn’t run so good. It appears a manual 97 has identical wiring diagrams but for 96-97 the diagrams are unique to this model. Z24 same year about 11k, the manual LS 17k!!! No wonder nobody wanted one as the manual option was so expensive. Quad four was originally a cosworth 2.3 design brought to the states and re engineered.
