97, 4.3 ECM Problems - Maybe?

[utahdanb]

Well here is the story: been having electrical problems when it snows and using the 4X4.
First case: 4X4 on, stepped on the brakes heard a clicking noise in the dash then received 2 codes IE: the camshaft sensor (high voltage) and the MAF P0101 (range performance). I replaced the cam sensor; code remained so I didn’t replace the MAF. Codes remained on.
Second case: 4X4 on, stepped on the brakes while taking it out of 4high, fuse 5 blew and the fuel pump quit running. Replaced fuel pump (after the pump was out verified that the pump still ran but only after smacking it around) replaced the BAD 4 prong connector for the power supply, fuel pump works, started the engine ran really rough like lunging and idling down in series. Received 3 codes P0101, PO108 & PO123 (MAF, MAP and TPS) having fun now.

Repair scenario: checked entire harness for shorts (no avail) checked entire chassis and dash for shorts (no avail) from a diagnostic tree I verified that the 5 volt reference that is associated with the MAP and the TPS from the ECM or VCM or PCM is non existent.

Now based on this information does it sound like I need a new computer or am I missing something.

Can my exisiting computer be reprogrammed or am at the Dealers Mercy????

[mike2004tct]

[quote=utahdanb Can my exisiting computer be reprogrammed or am at the Dealers Mercy???? [/QUOTE]

Can't help too much with the problems your having, but I have had my ECM replaced.
If this is the way you end up going, here's a suggestion to avoid a Dealer/Stealer;

If you have a NAPA store nearby, try them. My local mechanic went to Napa for a rebuilt ECM ($200.00) and Napa flashed the program for another $125.00.

One other electrical area of concern is the Ignition switch, particularly on '97s. Although I've also had that problem, it caused a complete failure, not the type of stuff you're talking about, And when my ECM failed, it was also completely dead, no error codes.

Good luck.
Mike

[old_master]

With no Vref being present, it would be best to get a flow chart and track down the problem before you just start replacing parts. If Vref is shorted to ground, and you connect another ECM, it will toast that one too, and the parts places don't like to warranty ECMs. Typically you buy it, you own it.

[utahdanb]

When I removed the associated connector (at the ECM) that supplies power to the TPS and the MAP and tested the 5 volt ref on the ECM it read .02 volts, then when I place the connector back on and turn the key the voltage to the sensors are 11-12 volts. I chased down these wires and did not find any obvious shorts. I had perfect ohms from the ECM connector to the sensor connectors. (Which only prove I was testing the right wires).
Forgot to mention: when I replaced the fuel pump a “coworker” did attempt to clear codes while the blazer was running, that’s when it started to run rough (didn’t mention cause it was a dumb dumb move) could that toast my ECM?

[nickledimed]

Originally Posted by utahdanb

When I removed the associated connector (at the ECM) that supplies power to the TPS and the MAP and tested the 5 volt ref on the ECM it read .02 volts, then when I place the connector back on and turn the key the voltage to the sensors are 11-12 volts. I chased down these wires and did not find any obvious shorts. I had perfect ohms from the ECM connector to the sensor connectors. (Which only prove I was testing the right wires).
Forgot to mention: when I replaced the fuel pump a “coworker” did attempt to clear codes while the blazer was running, that’s when it started to run rough (didn’t mention cause it was a dumb dumb move) could that toast my ECM?

Depends....how did he try to reset the codes?.....did he unplug the ECM and replug it back in while the truck was running?...if so...yup...its toast.

[utahdanb]

No he did it with a diagnostc tool, one that he had, very high tech, you needed to place the vin number in it for it to work, not like my $80 cheap reader.

[utahdanb]

All right here is the deal,
Why the ECM got screwed up is still a mystery, however it was intermittent, I believe it has to do with the fact of snowy/wet conditions, 4X4 is engaged, and the antilock brakes were applied all at the same time. My thoughts are a short in one or all of the components, or I had a faulty ECM that couldn’t handle the load????

I got a remanufactured ECM from NAPA for $125 and had the local Chevy dealer flash the program on to it for $45. (All of this language was unknown to me a week ago)

I wanted to thank all those how responded to me and gave their opinions.
Without this site I would still be on the side of the road or in jail for lighting my car on fire on the side of the road.

Thanks again.
Dan