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PCM Problem or what?? NEED HELP ASAP!!


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Newsom09's Avatar
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March 12th, 2011, 9:19 PM   #1  
PCM Problem or what?? NEED HELP ASAP!!

Well I have a 96 4x4 tahoe and it's confused me so badly lately. First of all, my speedometer won't work, my ABS light is on, my service engine soon light is on and when I plug my code reader up to check the codes, the reader says NO LINK. As far as the speedometer and ABS light, I have done some research and found out that along with making the speedometer stop working, the Vehicle Speed Sensor sends signals to the ABS system and if it goes bad, it will cause the ABS light to come on. Well I traced the wires from where they plug into the sensor all the way to the PCM and coudn't find any bad wires or anything and I replaced the Vehicle Speed Sensor today and it didn't fix the speedometer and the ABS light is still on. And like I mentioned in the first of the thread, my service engine soon light is on and my code reader says NO LINK when I plug it up. So does anyone know if it is the PCM or if not, does anyone know anything else that it could be doing all this??

 
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March 12th, 2011, 9:46 PM   #2  
Could be but have you tried a re-boot? disconnect the battery and short the disconnected terminals together, wait about 10 min and give it a go...
Make sure any aux batteries are disconnected prior to shorting cables together....

 
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March 12th, 2011, 10:31 PM   #3  
if you didnt find any exposed wires in the entire harness the PCM may be bad. Take it out open it up and smell it for burn connections. they tend to have a rubbery smell. The PROM may be good but the circuit board may have fried.
check the ground wire as it goes from the PCM to the ground station.

 
Newsom09's Avatar
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March 12th, 2011, 11:02 PM   #4  
When you mention the reboot and shorting the terminals together, are you talking about shorting the positive and negative cables together?? and when and if it resets, what all will it do as far as the SES and ABS lights, speedometer and obd2 plug??

 
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March 13th, 2011, 12:52 PM   #5  
Yes to shorting them together after disconnecting all power sources, and it should clear out any codes, as for the function of the datalink connection who knows.. but it will at least give you a fresh place to start by clearing out any old data and anything that comes up new will need to be addressed...

 
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March 13th, 2011, 8:51 PM   #6  
Well today I put the cables together to reset the codes and when I put the battery back on and started my tahoe up, the SES light was off but it came right back on about 5 or 6 seconds after I started it. As far as taking the PCM apart and smelling for a burned smell, I did take it apart and I could smell a slight burned smell but nothing strong and nothing looked burned or black or anything on the circuit board as far as I could see.

 
EinST's Avatar
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March 13th, 2011, 9:35 PM   #7  
Is it possibly a DLC power problem? Make sure pin 4 is ground and pin 16, battery voltage (from Aux Pwr fuse)?

 
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