PCM went out, now all electrical is messed up, ABS always on, misses/dies
10-23-2006 | 05:07 PM
#1
PCM went out, now all electrical is messed up, ABS always on, misses/dies Basically my friends 98 TA had some random electical issues where it would occasionally slightly mis or the gauges would jump (not often but every once in awhile). He mentioned it acted a little funny but ran fine.
About 2000 miles later it just suddenly died. I ran HPtuners and it would scan but not take a program. I figured PCM went out.
New computer installed at the dealer and the car fired up and ran.
But now it has serious issues and cant figure out whats causing it.
1) Car will occasionally cut out or just instantly die when idling. If above idle it wont cut out long enough to kill the motor but its long enough to kill it at idle
2) Dash gauges (rpm and speedo) will jump all over place randomly. sitting with key on with even the engine off they will occasionally jump to 20-30 mph and 2-3k rpm. While running they will bounch or jump sitting at idle randomly. Not constantly but at least every minute. I mean they fluctuate all over alot, obviously electrical problem.
3) No PCM codes relating to the problem while running or logging
4) Low Trac light comes on pretty much everytime you touch the brakes as well as the ABS inop randomly. And the ABS is activated all the time. Even slowing from 10mph to a stop the pedal pulsates and the ABS is engaged.
5) I have checked all the wiring for burns/cuts/loose or missing grounds. This includes everything I can see on top and below the engine.
I'm to the point where I think the entire engine wiring harness needs to be replaced.
About 2000 miles later it just suddenly died. I ran HPtuners and it would scan but not take a program. I figured PCM went out.
New computer installed at the dealer and the car fired up and ran.
But now it has serious issues and cant figure out whats causing it.
1) Car will occasionally cut out or just instantly die when idling. If above idle it wont cut out long enough to kill the motor but its long enough to kill it at idle
2) Dash gauges (rpm and speedo) will jump all over place randomly. sitting with key on with even the engine off they will occasionally jump to 20-30 mph and 2-3k rpm. While running they will bounch or jump sitting at idle randomly. Not constantly but at least every minute. I mean they fluctuate all over alot, obviously electrical problem.
3) No PCM codes relating to the problem while running or logging
4) Low Trac light comes on pretty much everytime you touch the brakes as well as the ABS inop randomly. And the ABS is activated all the time. Even slowing from 10mph to a stop the pedal pulsates and the ABS is engaged.
5) I have checked all the wiring for burns/cuts/loose or missing grounds. This includes everything I can see on top and below the engine.
I'm to the point where I think the entire engine wiring harness needs to be replaced.
10-23-2006 | 06:25 PM
#2
First things first. Power. The one thing I can't stand about GM vehicles is the side post battery terminals. Down south with temps as high as they are batteries quite commonly boil over and that acid will eat away the positive cable and cause gremilins such as you describe.
1) The cable might not appear f'd up at first glance. Is the connector bolt ate up? Usually a dead giveaway.
2) The ABS computer is a seperate animal but does talk to the PCM. Having both just die at the same time...buy a lottery ticket now.
3) Flakey power would explain everything you have described so far. I had to replace mine a couple of years ago, now I just change the battery every 2 years regardless of what it is doing. The mess, the hassel of having the vehicle just up and die-no warning like the old days of weeks of "I gotta replace that battery" hard starting crap. The cable is a 4way setup.
A) Battery
B) Aux post
C) Starter
D) Alternator
Replace the whole thing and the battery if you find any corrosion and the battery is old. If no other maintenance, mods have been done to the car then this would work it's way up higher on my list.
1) The cable might not appear f'd up at first glance. Is the connector bolt ate up? Usually a dead giveaway.
2) The ABS computer is a seperate animal but does talk to the PCM. Having both just die at the same time...buy a lottery ticket now.
3) Flakey power would explain everything you have described so far. I had to replace mine a couple of years ago, now I just change the battery every 2 years regardless of what it is doing. The mess, the hassel of having the vehicle just up and die-no warning like the old days of weeks of "I gotta replace that battery" hard starting crap. The cable is a 4way setup.
A) Battery
B) Aux post
C) Starter
D) Alternator
Replace the whole thing and the battery if you find any corrosion and the battery is old. If no other maintenance, mods have been done to the car then this would work it's way up higher on my list.
10-28-2006 | 09:07 PM
#5
hook up a analog volt meter to the pcm 12+ to 12- and watch it,i'll bet you have power off and on.The analog volt meter will show it as the meter will sweep back and forth slightly if the is a open connection.Digital meters can't read fast enough to show you this type of problem.
