97 K1500 mystery "service engine soon" question

I've got a regular cab 97 K1500 with about 90K miles. Runs great! Every once in a while I'll notice my gear selector light is off, no tach, and no speedo (all other gauges work) then service engine light comes on. The
tach, speedo, and indicator light usually come back on the same day, but service engine light stays on for about 2 more...then goes off. Difficult to get a reading from AutoZone since it seems to be hit-n-miss, but got lucky last week. AutoZone man said 5 tranny codes came up, but didn't share them with me. Tranny does feel like it slips when light, speedo, and tach are dead, but feels fine when they come back on. 4X4 works great! It has been really cold lately and truck stays out in it 24/7. I'm baffled!! Any ideas?!?!?!?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

share
Any
Get the codes read again, and this time, get the ACTUAL codes.
Doc

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Service engine light is off again, but I'll try to catch it again when it happens.
Thanks!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The codes are stored in the PCM for a certain amount of time. The light doesn't need to be on to get the codes. Plus, the AutoZone dude probably didn't clear them after he read them and they can be still be retreived.
Doc

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
#1 Check battery connections, clean if necessary #2 The codes don't really matter- I bet they're all trans electrical codes #3 If and when it happens again, check for voltage at the trans fuse, the voltage probably won't match battery voltage and that's your problem
Do you notice the vehicle being in second gear and not shifting when your gauges don't work?
If cleaning the battery terminals doesn't work, try this This is what I do on 96 and newer- all work done under the dash. Bare a spot on one of the red wires(12v constant) and bare a spot on the pink, all wires are part of the ignition switch harness, cut the white wire in two. For the relay post 86 goes to ground, post 85 gets connected to the bared pink wire, post 30 gets connected to the cut white wire running away from the ignition switch, post 87a(if its not on relay just tape up the white wire on the switch side of the cut)to the white wire ignition side, and post 87 gets connected to a 10 amp fuse and then to the bared red wire

share
Any
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Went to AutoZone today, but light wasn't on and no codes were displayed.
The shifting thing you described seems to be what it's doing. Everything has been good for a couple of days now.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Print out the rest of my post in case someone tells you you need a new ignition switch, only a 10 dollar relay compared to a $100+ ignition

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Jeff & Missy wrote:

This exact situation happened to my 1995 ext cab Z71 last year. Turned out to be one of the crimped connectors in the wire harness attached to the ignition switch that had been broken by the action of using the tilt wheel function over the course of time. The broken connector would sometimes separate when bringing the tilt wheel down to the position I drove at. When tilting back up it would always make connection again. I always start my truck with the wheel up & then bring it down to drive. I got lucky finding it I guess. Put the key in the ignition, turn to run (don't start it), tilt wheel up & down while grabbing the harness near where your knees would be while driving. As you move it all around look for your shift position indicator light to flicker. I could have soldered it to make a repair but my truck has 220,000 miles on it so I replaced the ignition switch/harness (it's a single part #) Problem solved.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.