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After watching Paul's video entitled "1998 Chevy Van 5.7 No Crank and Misfire Troubleshooting" I am pretty sure several drivability issues over time(latest being misfire condition) may be traced to the PCM which, while not quite as corroded as the one in the video, is in pretty bad condition none the less(this vehicle sat around a lot in MI weather). GM put out a Service Bulletin in '04(?) which(while replacing bad PCM) required installing a redesigned PCM bracket/deflector to prevent water intrusion, these new parts were never installed on this vehicle, and to my knowledge may not even be available any longer due to the age of the vehicle(salvage yard?). Anyway, Paul had an excerpt in that video that he mentioned doing additional diagnostic tests later on to actually verify the diagnosis as a bad PCM . I do not have Pauls premium access but I assume the tests he performed were using his scanning equipment, something I do not have, or would not have any knowledge of using anyway. So are there other more "old style" methods to determine a bad PCM(particularly for my current misfire condition)or is this beyond my scope(no pun)to troubleshoot? Also, should I decide to just attempt a "part swap" on a used PCM, would it still require programming from a dealer/other, even if I match up the serial/code(16263494/CMUC)? Thanks .
Man, I went around the block one of these vans before....
Hollander interchange software says almost ANY gm PCM will work as long as you change the eprom (I've never tried that).
Unless, you've got a 3500 with a 4l80 trans, then it's a much narrower interchange. But you've got a 5.0, so it's probably a 1500 with a 4l60.
The only trick to make it run with the new PCM is a 30 minutes security relearn. That involves turning the key on for 10 minutes 3 times.
As far as checking the PCM, you'll need a diagram and a meter.
You'll need to know why the engine is missing before you can determine if the PCM is to blame.
For example, are you losing spark, losing injector control?
Those are only a couple examples of what could be causing a misfire that could potentially be traced back to a bad PCM or corroded connector.
Thanks for the reply Noah. Yeah, it's a G2500 with 4L60E. All I've done so far is put a spark tester on #2(cheap OBDII showing a P0302 DTC, Torque App also shows P0302, while also showing misfire on #1, but no code and not nearly as many counts). The spark test on #2, it "seemed" to be getting good/consistent spark, but I really don't have enough experience to know for sure. Guess next I'll do a fuel pressure/bleed test(spider-injector/pressure reg. leak/???).
I've got the 4 volume GM service manuals for the van(after the notorious lower intake gasket failure), has wiring diagrams(though my "skill" in that department have probably faded over the years).
Reason I suspect a PCM issue is that the rough idle condition started about a week after I pulled/(carefully)cleaned the PCM after I experienced a power/shift loss which included a stuck at 55 speedometer. I pulled/cleaned the VSS and those issues went away, but a week later the rough idle/misfire took place. I also suspected bad grounds due to rust, which I thought had been the issue with intermittent no crank/no start over the years, and so went ahead and cleaned the grounds...well, most anyway.
The manual states that for "replacement" of the PCM the following is required
. If the VCM is being replaced the Knock Sensor(KS)must be transferred to the replacement VCM.
. The replacement VCM must be programmed before the vehicle will run.
. The replacement VCM must have the Passlock Reprogramming procedure performed before the vehicle will run.
. The replacement VCM must have the CKP System Variation Learn procedure performed or a DTC P1336 will set.
Also...
. Ensure that the VCM being installed is the original VCM, or that the replacement VCM service number is identical to the original VCM service number.
Nothing about the EEPROM, other than it requires programming after installing replacement.
Pardon my stupidity, but am I right in assuming the EEPROM is a separate board component from the Knock Sensor module, and that it too has to be removed from old VCM to new VCM? My original post included the serial/code for my vans VCM, though I got the serial from a local dealer, as the sticker that contained that info must have blown off the crusty VCM case
No eBay APP ID and/or Cert ID defined in Kunena configurationEEPROM is electrically programmed. PROM is the chip that you swap out on older pcms.
I believe you can use a used pcm but I don't remember if the theft will relearn with mismatched vin #s. You can program used PCMs with a new vin on those ones though.
I would try to figure out what exactly is causing the misfire to happen first but used is an option.
Spark appears good, fuel rail pressure good/no bleed down. Fuel trims -13/-15 give or take(umm, torque app). 3 days after last rain, noticed RED PCM connector(fuel injector pins)was a little wet still. Going to pull the spark plug, maybe compression check, switch wires out, check dist. cap, etc...but still leaning towards bad PCM ....unless you guys can suggest other checks before trying a PCM swap.
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