Another 'service 4wd' Issue

[matthuber1]

Alright, so i am a new GM owner. Just purchased a 2005 GMC Sierra with push button 4wd, and i started it up yesterday morning and the 'service 4wd' message appeared on the info center. When this happened at first, all of the lights on the 4wd switch cluster turned off. I got to my destination, did my business, and started the truck back up... only to find it is stuck in 4wd low, and the 4wd low light is on. On the (slow) drive home it was switching between low and high gearing intermittantly. I came in an read all of the relavant topics on this site and started and stopped the thing a few times until only the neutral light was on. At this point the truck felt like it was in 2wd. i drove it arount the block, stopping and starting in a few places and pressing 2wd high repeatedly. Finally got the 2wd light on. Ran fine the rest of the day. Last night service 4wd came on again.

 

I try pounding on the dash, i pulled the cluster out, all of the solder joints appear ok. It was 90 degrees and sunny all day yesterday, so i dont think the TSB applies.

 

Any ideas?

[Ranger]

Search for bad 4wd switch, it's either a bad contact or the whole switch assembly crapped out...Replace it.

[5Alive]

Have your truck scanned by a Tech II to pull the codes. A code has been set since the service 4WD message lit up.

 

Any OBD-II cabable code reader, software, or digital guage will NOT necessarily read chassis codes. The DTC codes you are looking for will begin with a "C", not a "P". For example, C0327 is one such trouble code, which often means the Encoder Motor sensor on the transfer case may need to be replaced.

 

If the truck still has a subscription to OnStar maintained, then OnStar will be able to tell you what the code is, if you ASK the operator to read everything that shows up on their screen. To the operator unfamiliar with vehicle diagnosis, the codes are just gibberish to them, that they don't normally read to subscribers. But since you now know that the codes you are looking for begin with a C, and will for the most part be in the 300 range, you can ask them to look for any codes like C03xx.

 

Or take it to a shop that has a SnapOn 2500 or better scantool, or whatever other professional class equivalents are out in the field these days. If you recently bought the truck from a dealer, maybe the dealer will scan it for you as a courtesy. Just get it scanned somehow, cause that will vastly narrow down what the root cause of the problem is, and beats beating on your dashboard hands down.

[matthuber1]

Thanks for the suggestions, I guess i will call onstar and get the subscription going for a month! Its cheaper than the $85 the dealer would charge me!

 

Wait... with the 'three months on us' promotion its free!!!

 

Great advise.

[matthuber1]

Update:

 

Called for my free subscription and got it... only now i cant get the message to come on. They said there were no codes. I will call back the next time the 'service 4wd' comes up.

[CKUBIK]

HEY MATT I AM HAVING THE SAME ISSUE AS YOU....... IT HAS BEEN INTERMITTENT FOR ABOUT A MONTH NOW. I HAVE EXPERIENCED A LOSS OF POWER AND WHEN I PUT THE ACCELERATOR TO THE FLOOR IT WOULD ONLY REV TO 2400 RPM. I ORIGINALLY TRIED TO REPLACE THE SWITCH AS MECHANIC FRIEND HAD NEW ONE AND RECOMMENDED, ONLY WITH NO LUCK.

 

I HAVE FOUND..........

WHEN I SHUT THE TRUCK OFF AND BACK ON AND THE INDICATOR LIGHTS SHOW IT WAS SUPPOSED TO BE IN 4WD LO, BUT IT WAS NOT BECAUSE I HAD NO TURNING BIND(COMMON TO BEING IN 4WD) THEN I PUSHED THE 4WD HI AND GOT IT INTO 4WD HI THEN INTO 2WD W/O ISSUE. I HAVE SINCE HAD THIS HAPPEN A COUPLE MORE TIMES AND BEEN ABLE TO SELF FIX BY TURNING OFF AND BACK ON.

 

I TOOK MY TRUCK TO DEALER 1 HR AFTER I GOT IT TO SHIFT BACK TO 2WD THE FIRST TIME AND THEY FOUND NO CODES WITH THE TECH 2 ON THE TRUCK. THE DEALER TECH TOOK THE TRUCK FOR A RIDE WITH ME AND WE COULDN'T GET IT TO ACT UP (OF COURSE) AND THEY DIDN'T KNOW HOW TO APPROACH THE PROBLEM UNLESS THE CAN READ A CODE. I HAVE A 2006 GMC VORTECMAX CREW CAB 4X4 WITH 43,600 MILES ON IT. PLEASE LET ME KNOW WHAT YOU FIND OUT WITH YOUR TRUCK AND I WILL DO THE SAME WITH MINE.

 

THANKS

COREY KUBIK