Limp Mode

[Truenorth]

I had a problem this morniing in which my truck 97 Sierra 1500 . My engine light came on when I started it and from that time I have not able to get out of first. Does this indicate limp mode or is my tranny shot?

[Truenorth]

Scanned it and found 2 shift solenoids reporting a problem. Thought that was strange that two would go at same time. Suspected my car starter/alarm to be causing the problem, so Icalled where I had it installed. They said that if I unplugged the battery the starter would of lost it's programming and when I used the starter it would of caused the truck not to shift out of first. Solution for this is to unplug the batteries again for 20 min or so and then start thr truck without the remote starter. Going to try that now....

[Phil Holmen]

I had the same problem with my starter the first time that I used it too. It is caused by only energizing the frist ignition wire and not the second. The second is required for the transmission.

[Truenorth]

Fixed back at driving over 35 mph. Remote starter was the problem. Need to get it reprogrammed again.

[ucdavis]

This has happened to me coupla times. I found that the computer needed rebooting. Shut her down, restart & drivability returns.

[JohnC]

Actually, limp mode is second gear. Enough to get you going, but 45mph sounds like the end of the world...

The problem occurs when you power up the PCM but the power to the trans (separate circuit) is either missing or flakey. The PCM feels it cannot reliably control the trans so it shuts off all the shift solenoids. All off is second gear. A common cause is a problem with the ignition switch contacts. A remote starter that did not power the trans circuit would cause it as well.