Tach stopped working- new PCM
08-18-2011, 06:06 PM
#1
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Tach stopped working- new PCM The tach in my 1998 SS stopped working, I took it to the dealer and they said that I needed a new PCM to fix it, and that it would have to be reprogrammed. Anyone had this happen to them. Thanks for the input.
08-18-2011, 08:17 PM
#2
i would check the wiring first and see if the tach is getting a signal. it may only be your tach that is bad and they are trying to sell you a pcm to make $ off you. check the wire at the tach and at the pcm to see if its a broken wire.
08-19-2011, 10:33 AM
#4
If it also starts hard and sometimes backfires its cam sensor problem and you should have codes for that. If their is problem with cam sensor the tach don't work. When I swapped in my erl ls3 based engine my tach didn't work.I had to reverse wires on the conversion harness they were backwards . Also year or so ago had problem intermittent with cam sensor codes it was connector on the engine harness this was pre 427 swap when had 408.
08-19-2011, 08:10 PM
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No problems with starting just no tach, skip shift works just no tach, I just don't know about the PCM part, but a buddy that owns a shop said it could be that the PCM part that controls the tach may not be working, just wish I had more info on this stuff. Well I will try the PCM, my buddy got me one cheap.
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08-21-2011, 01:26 PM
#8
This is a common problem with the 98 PCM's and yes, sometimes a PCM replacement is needed. Sometimes the tach pulses inside the PCM will quit sending, and the gauge will no longer get a signal.
Get someone with a good scanner to check your cam position sensor and crank sensor. If those 2 sensors are working properly, then you've got 1 of 2 problems. A break in the wire between the PCM and gauge (unlikely unless you've taken the dash apart), or the tach pulses in the PCM are dead.
If you have a good voltage meter, you can check continuity on the tach wire coming off the PCM as a last resort.
Had this happen on many 98's. The 98 PCM's suck beyond all belief. Now would be a good time to convert over to a 99+ pcm.
Get someone with a good scanner to check your cam position sensor and crank sensor. If those 2 sensors are working properly, then you've got 1 of 2 problems. A break in the wire between the PCM and gauge (unlikely unless you've taken the dash apart), or the tach pulses in the PCM are dead.
If you have a good voltage meter, you can check continuity on the tach wire coming off the PCM as a last resort.
Had this happen on many 98's. The 98 PCM's suck beyond all belief. Now would be a good time to convert over to a 99+ pcm.
08-23-2011, 09:24 PM
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you should be able to swap with your buddys f-body PCM car will run fine and if your tach starts working there right. as a professional technician I will tell you the majority of us will not take the time to check wiring, we will check for crank signal and see if the tach sweeps upon start up, if yes then its gotta be the PCM if a new PCM dosent fix it then i will dive into wiring issues. sorry that just how its done in the shop.
