Hi van folks! My 04 Chevy Express 2500 cargo van has 94K miles and runs like a champ. I hit an 1000 pound elk cow on the left corner that took out the grill and head light but no mechanical problems for over 500 miles. Then upon starting the dash shows abs and brake warnings with 4 extra warning chimes. Drives normally otherwise for 30 seconds then bouncy speedometer, 33 more warning chimes and transmission goes into limp mode (erratic shifting 40 mph max or so) Replacing the speed sensor provided a temporary cure but brake, abs and speedometer trouble returned to the dash shortly after the fix but no limp mode. 300 miles later limp mode comes back. That was 2 weeks ago. Now it runs perfect like nothing ever happened but I'm just waiting to be stranded again and it won't misbehave for a mechanic. Help!
Intermittent transmission limp mode
- Thread starter Brian F
- Start date
Help Support Van Living Forum:
bob91yj
Well-known member
Which speed sensor was replaced?
B and C
Well-known member
Our Tahoe had the ABS light come on but when I found a daytime running light on the front out and replaced it, the ABS light went out. YMMV
bob91yj
Well-known member
It's possible that you have a wheel speed sensor that has failed causing the ABS/brake lamps coming on...doesn't explain the speedometer dropping out though. I worked at GMC dealership for 14 years, the instrument clusters on the 00-06 models were notorious for failing in the Yukons/Sierra's, I didn't see enough vans to know if they had the same issues. You may have two different issues.
Code readers can be purchased for less than $50, you may want to consider purchasing one so that you can read the code when the condition occurs. Having said that, most shops will be reluctant to make a repair based on the customers diagnosis, if attempt a repair based on your diagnosis, the shop doesn't want to be responsible for making the repair if it doesn't solve the problem.
Code readers can be purchased for less than $50, you may want to consider purchasing one so that you can read the code when the condition occurs. Having said that, most shops will be reluctant to make a repair based on the customers diagnosis, if attempt a repair based on your diagnosis, the shop doesn't want to be responsible for making the repair if it doesn't solve the problem.
bob91yj
Well-known member
Most AutoZone stores will also scan for codes for you at no charge.
highdesertranger
R.I.P HDR
- Joined
- Apr 4, 2012
- Messages
- 22,892
- Reaction score
- 87
just having a list of set codes is not enough. you need to know what to do with the information. as an example you don't just star replacing parts because a code was set, you must diagnose the issue. the diagnosis flow charts will send the inexperience person down a rabbit hole.
as a side note auto parts stores in California are not allowed to read codes for you. highdesertranger
as a side note auto parts stores in California are not allowed to read codes for you. highdesertranger
Bridgestreet
Member
- Joined
- Jul 5, 2018
- Messages
- 21
- Reaction score
- 0
bob91yj said:
I got a $50 code reader for my Sprinter. It was spot on and I stuck to it and found the electrical short it pointed me to. The short was stopping the Wastegate valve from operating. I fixed the issue for free myself. Tiny pinhole in wire insulation.
Sent from my iPhone using Tapatalk
Bridgestreet
Member
- Joined
- Jul 5, 2018
- Messages
- 21
- Reaction score
- 0
The codes get more and more specific dependent on the complexity of the reader. A broad code gives you general direction, better readers more and more specific.
Sent from my iPhone using Tapatalk
Sent from my iPhone using Tapatalk
bob91yj
Well-known member
You have to start the diagnosis somewhere. Scanning for codes is a starting point.
Curious what hidesertranger would suggest as a starting point.
Curious what hidesertranger would suggest as a starting point.
highdesertranger
R.I.P HDR
- Joined
- Apr 4, 2012
- Messages
- 22,892
- Reaction score
- 87
if you think I was suggesting ignoring the codes was the way to go, I am sorry that is not what I meant at all. I was just trying to get across that the code reader is not the end all, you still need to test, diagnose, and follow troubleshooting flow charts. I seen a lot of people waste a lot of money replacing parts because of codes. even sadder most of the time the parts are replaced with parts of inferior quality. highdesertranger
bob91yj
Well-known member
^^^^Fair enough, and agreed, trouble code gives you a starting point.
Basic trouble shooting for electrical circuits always begins with fuses and circuit breakers and making sure everything has power that should, when it should. Basic maintenance requires cleaned and checked grounds. With those out of the way check wiring connections and harnesses. Intermitent problems often happen because a harness moves or is flexed, think connectors, brackets or wire harnesses that may be out of place, streched, or pinched from impact with elk pieces or pieces of metal bent by elk pieces. I believe that some scanners are able to record events as they happen. You might ask your mechanic about that as well if it were to happen again it would help to "see" what was recorded. Recorded codes can point you to a certain componet or circuit. For example a code for a bad sensor may actually be a broken or pinched wire or bad connection in the circuit that goes to that sensor which is still perfectly good. Since things seem to work sometimes means things like was it on a hill under aload flexing the drive train or only when slowing down or when cold will make it easier for the mechanic to replicate what the vehicle was doing when the problem occurs so pay attention if it does happen again. Maybe moving the harness to the speed sensor when it was replaced made it make contact and work for a while till heat caused it to expand and when it cooled down and made contact it worked again. Round pin connectors are famous for that. Good luck and let us know what happens and why.
