2002 Chevy Impala Will Not Crank, Will not communicate

Tiny
DNDPROVOST
  • MEMBER
  • 2002 CHEVROLET IMPALA
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 250,000 MILES
I was working on an overheating problem with this vehicle and among other things changed out the upper and lower radiator hoses. The upper hose change required me to move the air box (with the ECM in it) to one side. This may or may not be related, but now it will not crank. I did some research, used a 2.2k resistor across the yellow and black passlock sensor wires going into the BCM, did the relearn process, got the security message to go away, and it still does not crank. After another battery disconnect/reconnect the security message has returned. What's more, it does not talk to my Innova 3140 code reader. I have confirmed continuity from the PCM to the DLC on the serial data line and the associated ground line. I have tried a different PCM (used). I am also getting a "service vehicle soon" message, and out of curious frustration disconnected the PCM from the vehicle and turned on the key. The results are identical, it's as if the PCM isn't there. I have confirmed 12VDC at the battery voltage pin of the PCM, and checked continuity to my ground points. The related fuses all look good. The big puzzle is why it won't crank, but I also don't understand why my reader can't talk to the PCM. I have a fairly strong electronics background, and am being tempted right now to go more into computers simply so this sort of thing doesn't floor me again! Any assistance would be appreciated
Saturday, July 31st, 2010 AT 4:45 PM

3 Replies

Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
Does engine rotate or does nothing when key is in start?

Hand held scanners generally will only read "P" powertrain codes and the PCM is a fused circuit.

So the diagnostic link connector fuse may be burned out, or the code is not readable by the scanner ("B" or "C" code).
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Sunday, August 1st, 2010 AT 7:51 AM
Tiny
DNDPROVOST
  • MEMBER
  • 1 POST
When the key is turned, the instrument panel goes dark and nothing happens. My scan tool does attempt to engage when I plug it in and turn the key on, but cannot contact the PCM. The B+ voltage is therefore at the DLC plug for my scanner, and I've looked at all the fuses that are in any way connected with the PCM or DLC.

So even if I'm in "security mode", my scanner should be able to talk to the PCM?
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Sunday, August 1st, 2010 AT 1:09 PM
Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
Even though you have voltage at ALDL connector if in security mode, PCM will not connect to scanner.

If security light is off and not flashing, scanner should connect.
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Monday, August 2nd, 2010 AT 9:04 AM

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