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Discussion Starter #1
Took the truck out yesterday, seemed to be running a little different looked at the dash and speedometer is on 0 check engine and ABS lights are on. This problem seems familiar but I can't remember from what. I will get it somewhere to pull codes but afraid to drive too far. Any ideas?
 

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Code(s) and truck info please
 

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Depending on the codes.... say if they are all transmission codes, you already dont have a speedo, do you have the prndl indicator light or not? Are you also starting in 3rd? I bet because you say the truck is running like crap....

So if you have 6-7 tranny codes, you dont have an indicator light and your starting in 3rd.... the tranny is in limp mode. Theres only a few problems that cause it.... could be as simple as a blown prndl fuse in the end of the dash, the big round plug has come undone at the tranny, you have a wiring problem on the pink wire which is also pin e on the big round plug, but this is doubtfully.

Usually it is caused by a faulty electrical ignition switch.

Pin e on the plug is the only positive connection to the transmission, all other wires are negative connections that get turned on or off to function correctly. Pin E should read the exact same voltage as the battery.

Since these are expensive I grabbed 3 from a junkyard and the first one I tried worked.

Good luck

Al
 

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If your staring in 3rd it's safe to drive, you should be able to manually start in 1st or 2nd to get going then manually shift to 3rd.

Man 60 000 miles? Gotta be a VERY nice truck!

Al
 

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Beautiful truck! Are you absolutely certain it's in 1st gear and not 3rd? Do you have the prndl indicator (gear selector) light on the dash?

Since you have such a nice truck and need some awnsers..... come check out www.gmt400.com it's a forum dedicated to these trucks only and not cluttered with new truck crap at all.

Take care

Al
 

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Discussion Starter #8
It is definitely in 1st, no light on my dash for gear selector. Guy where I get my state inspections done gave me his scan tool to pull the codes. I will check out that other site. Thanks
 

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Its 3rd if you have no gear selector. No power whatsoever but the truck will drive. Check the prndl fuse in the end of the dash? #18 or 19 I believe. If that checks out make sure the plug is plugged into the tranny. Get a 14mm or 15mm socket and remove the heat shield on the side of the tranny so you can easily see the plug. Clean this area thoroughly before unplugging it, although I bet its spotless on your amazing truck! Look at pin E on the plug and corresponding terminal on tranny. They are probably Absolutely fine, check the voltage on the plug at pin E. If it's not Exactly the same voltage as the battery, and all the wiring checks out, I'm sure it will as it usually is fine inside a wire loom, you will need a new ignition switch.

Al
 

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There is no other way to diagnose a faulty ignition switch that I know of. They can fail a few different ways but this seems to be the most common.

Al
 

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Well I will put my foot in my mouth. Lol. Its very interesting to not have the PRNDL indicator light as well.

The speed sensor correlates with the throttle position sensor to dictate when to shift. You may just need a new vehicle speed sensor, or its wiring may need a look at. it's in the tail shaft on a rwd or on the transfercase of a 4x4.

Al
 

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I'm sorry for misleading at first. Glad you got a scanner to get straight to it. If the VSS can not determine the speed of the vehicle, the abs system can not function correctly so you get the abs light.

Al
 

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Discussion Starter #14
Going to look at it tomorrow wires, plug etc. Prices on them are all over the place $9 to over $100. Found a lifetime warranty one for $31.
 
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