1999 GMC Sierra 1500 Tachometer

  • 1999 GMC C1500

1999 GMC Sierra 1500, 4.3L Vortec, 86400 miles
I bought this pickup last week. At first, everything was working good. About four days ago, the tach dropped to zero and a few moments later the SES light came on. After a bump or two the tach jumped back up and the SES light eventually went off. Over the next couple of days this continued to happen until finally the tach quit and the SES light stayed on constantly. I noticed that the SES would only come on when the tach was zero. The diagnostic codes were P0102 and P0340. After changing the camshaft sensor and erasing the codes, the tach still doesn't work and the SES light remains on. The codes are still the same. After checking the fuses and noticing a lot of?Corrosion? I changed out almost all of the fuses under the hood. I have also checked the connectors on both the camshaft sensor and the crankshaft sensor. The only thing that I can come up with is a loose wire somewhere that affects the tach and keeps throwing the P0340 code. All of the other gauges are operating properly and the only other complaint that I can note is that the transmission shifts a little roughly. The wiring diagrams that I have are a little vague to me, and all I can roughly get out of them are that the tach signal wire is white and that it is the A2 position on the instrument cluster plug-in. I know that it connects through the VCM, but from there I can't seem to figure out where it goes. I am hoping that my problem is just a loose wire somewhere, and I hope that someone would be able to help me with this problem. Thanks in advance.

Do you
have the same problem?
Tuesday, September 12th, 2006 AT 5:32 PM

1 Reply


Yea it sounds like a wire problem.I hate those little buggers.

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Thursday, September 28th, 2006 AT 4:26 PM

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