alero 2000 3.4 v6 electrical issue

[steve]

my daughter has an alero 2000 3.4 v6 and when you put the key in the igintion
the dash gauges went mad ie 220kmh,temp gauge hit maximum even though the car
wasnt started.

the car doesnt crank over or no clicking from the start/solenoid either

so i checked the battery terminals….excellent condition
cleaned off the grounds by the battery.battery is fully charged up
cleaned off the ground to the engine

still the same.

so i changed out the ignition switch.still the same.
i have checked all the fuses concerning the cars computers and the fuses for the ignition
and all of them are perfect.

i got someone to plug in an OBD reader to check for any codes and the reader
couldnt find the computer,there wasnt any power from the ignition to power
the reader.

i havent got round to checking the fuses for the windows,ciggie lighter or mirrors
(i am led to believe the ECM is on the same circuit)

have i got a ground issue with the ignition?
how would i check this out.

Topic

[redfury]

I’d suspect the PCM in this case. If it were just a ground issue, it would possibly affect one of your problems, but not that many unless it were the battery ground itself. Check voltage from the battery post to a ground and see if that reconciles with voltage across the posts.

[James O’Hara]

Definitely sounds like a def computer issue. I would check the power and ground for PCM/ECM aka not at the battery. You may also want to check the relays. I know you said fuses but, there is normally a relay for the PCM/ECM.

[steve]

[quote=”MDK22″ post=121680]Definitely sounds like a def computer issue. I would check the power and ground for PCM/ECM aka not at the battery. You may also want to check the relays. I know you said fuses but, there is normally a relay for the PCM/ECM.[/quote]

so were would i be able to check the power and ground at the ECM?

i do believe i have the ECM half ripped out already as its located in the drivers side
footwell.( it was -25c when i started all this)
and just re checked the 3 fuse box diagrams for the alero and NO relay to
found for the ECM.

all PCM and body computers have 10a fuses.

[Glenn]

Before you condemn the PCM, check the battery amperage again. I experienced the exact same symptoms with my GM 3400 and it wound up being the battery. If I am remembering ( it was a while back) the battery tested as good when this symptom occurred. Hiow old is the battery?

[steve]

the battery is around four years old.

i tried to charge it with one of those smart chargers and it told me
the battery was full and all cells are good.

[Glenn]

It may not be the battery. I’m only speaking from prior experience with my GM 3.4. I thought for certain the PCM had lost it’s mind. It was the exact same symptoms as you described. Maybe you could have the battery tested at a shop under a load. This battery has already been in use 48 months, so you might want to check further. Good luck…

[Author]

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