Question about 1997 Pontiac Grand Am

1 Answer

Shift Indicator Module PRND123 illuminate, but LED for each position do not light up

I'm working on my wife's car to get all the issues worked out and make it function normal again. One issue I'm working on now is for as long as she can remember, the shift module for the transmission has not worked. The LED on the left side that illuminates the letters PRND123 works, so I know there's voltage coming in. However, there are multiple LEDs on the right side, one for each drive position, indicating whether you're actually in Park, Reverse, Neutral, Drive, etc., and these lights do not work. None of them work regardless of any position the shifter is in. We can assume voltage is going to the module, I can attest there aren't any driving effects that I could notice, so no issues with the PCM. That probably means that the circuitry on the module board itself, one of the components has failed, most likely one that detects a certain amount of voltage and lights up the correct LED? If anyone has a suggestion on how to troubleshoot that at home, that would be great. I have taken photos of the front and back of the circuit board and created an overlay of the two to aid in tracking down the component circuitry on the board. The last resort is eBay since nalleygmc doesn't stock this part, or the junkyard, but without being able to start up the car, it would be a hit or miss chance one from the junkyard would even work. Thanks! Jeremy

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  • jeremy_swnsn
    jeremy_swnsn Feb 22, 2012

    I metered the voltage coming from the wire harness, all lines receive voltage, so at this point, I'll assume the wires are not corroded. I've done some testing on the board itself, finding pin 8 of the onboard chip being ground. It looks like the chip is responsible for somehow determining (via signal from PCM?) what LED to light up and grounds that LED. The power side of the LEDs are all connected to a common rail. Also, it's been ruled out that the PCM is sending voltage or resistance information to this module to determine what gear the car is in, rather it's probably some sort of data code. I've tracked down some information through Chilton that shows perhaps the signal may be originating from PCM C2-16 (Vehicle Speed Out to Inst. Panel/Conv. Center and Cruise Module). The chart indicates it should be a Dark Green/White wire. I'll crack open the tape and see if this is the color of the wire. Either way, it's a new direction to start from. Chime in anyone, please!!!

  • jeremy_swnsn
    jeremy_swnsn Feb 23, 2012

    The third wire (besides the red-hot and black-ground) is tan. That rules out the PCM C2-16 circuit.


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This is a common problem and the issue is with the display of the gear selector, it must be replaced. You will need to remove the cluster form the car and send it into a GM approved repair center for replacement of the display.

Posted on Feb 23, 2012

Testimonial: "This is an appropriate answer for where I posted. I should probably post in the electronics section if I'd like help troubleshooting the board itself. Agreeably, some people will probably just seek an answer such as to simply replace a part. Others, of course, may ask to forego that route, maybe in the case of discontinued parts and such or to not simply (spend money), which is too often the easiest answer. Dennis' answer is very valid and hopefully can help out if others end up on this page. For my particular situation, I'll continue to search for an answer to fix the board on my own, armed with electronics know-how and a multi-meter and hopefully a circuit layout to help aide in knowing how this thing is supposed to work and replace the malfunctioning component, which is all a GM repair center would do, the only difference is they have access to the service information for this part! Thanks again :)"

  • 1 more comment 
  • jeremy_swnsn
    jeremy_swnsn Feb 24, 2012

    Hi Dennis,
    Thank you for your suggestion.

    I had gathered this was a common issue. Is it your opinion that the problem is the module itself and replacing it with a known working module will fix the issue? I did locate a seller on eBay with a superb rating and they say it indeed works, part is $30, much cheaper than sending it in for replacement.

    I do understand that you're trying to help and I deeply appreciate it. I was here at Fixya (do-it-yourself) mainly because I possess a good deal of mechanical and electronics knowledge and was hoping for a more in depth solution, whether it can be said that the IC on the board itself is the most common thing to fail or some other part such as a resistor or such. It's highly unlikely all the LEDs would fail. Also, I've had difficulty tracking down an electrical schematic for this board, it's not in the Chilton's Manual unfortunately, although, I've tracked down what I hope to be the original manufacturer of the part, Invotronics Mfg. out of Canada, I even got the Patent Number 5,245,313. My next step was to track down contact info for the company and see if they'll be nice enough to email a schematic or see if a patent search will yield this information.

    Again, thank you for your insight, it's much appreciated!

  • yadayada
    yadayada Feb 24, 2012

    Yes a new module will fix it 95% of the time. This is a common issue with all models that use this gear position display, Buick, Chevy and Pontiac mid sizes. Please rate my help for Fixya. Thanks

  • yadayada
    yadayada Feb 24, 2012

    You are getting way to deep into what is a simple problem of a faulty disply, we don't fix these at the dealer, they are boxed up and sent in for repair. You check the signal from the transmission range switch with a scanner and if its there and no display the problem is the display. What you are doing is a huge waste of time and we would loose money on every job.


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