Emergency Help stuck on Road!

Hi everyone. I had to get a hotel tonight because my truck decided to act strange. We are going home from Phoenix and here are the symptoms:

First, I have a 2003 Silverado 2500HD with the duramax/ allison transmission.
We were cruising at 65 mph in rainy conditions when all of a sudden the truck made a warning beep and said "service brake system". The abs and brake lights were then illuminated. The truck immediately kicked out of cruise and sounded like the engine braking system was engaged. Also, the speedometer starts wavering +- 5 MPH after it hits the magical 45 mph threshold. We had been traveling through rain for several hours without any problems whatsoever.

We tried to restart the truck and found that all the codes would stay off until we hit 45 mph. As soon as we hit 45 mph, no matter what gear we were in, the service brake system light and abs would come back on.

It is easter sunday, so nothing is open and we are still 1000 miles from home. Any help in diagnosing the situation would be greatly appreciated.

Nick

Hi everyone. I had to get a hotel tonight because my truck decided to act strange. We are going home from Phoenix and here are the symptoms:

First, I have a 2003 Silverado 2500HD with the duramax/ allison transmission.
We were cruising at 65 mph in rainy conditions when all of a sudden the truck made a warning beep and said "service brake system". The abs and brake lights were then illuminated. The truck immediately kicked out of cruise and sounded like the engine braking system was engaged. Also, the speedometer starts wavering +- 5 MPH after it hits the magical 45 mph threshold. We had been traveling through rain for several hours without any problems whatsoever.

We tried to restart the truck and found that all the codes would stay off until we hit 45 mph. As soon as we hit 45 mph, no matter what gear we were in, the service brake system light and abs would come back on.

It is easter sunday, so nothing is open and we are still 1000 miles from home. Any help in diagnosing the situation would be greatly appreciated.

Nick

Check speed sensor or sensors and wiring plugin to them.
If a auto zone or O'reilly store around they will read codes for free and may have some repair info.
AZ has All data repair info.
Post back any code no you may have.
Good Luck

There is also a possible loss of communication with the ABS module, or problems with the ABS power supply or power relay. Scanning would be the fastest method of diagnosing the problem, but checking all fuses and for signs of moisture intrusion into connectors might also be prudent.

The EBCM is mounted to the inside of the left frame rail, right about under the driver's floor section. The electrical connectors and ABS power relay there could be wet.

http://arrc.epnet.com.oh0049.oplin.org/autoapp/CHEVY_CK-PICK_99-07_F/p5images/C/chevy_aval15_02-04_ehcuL.gif

Yeah I looked under there and it all looks clean and free of water. I am thinking this may be related to a drivetrain vibration I have started experiencing. I limped the truck to a larger town for service tomorrow. It started out as a vibration above 65 that sounded like a 4wd that is full timel. As the miles kept going by, eventually the vibration became louder and now it vibrates clearly and loudly, accelerating or decelerating all the way down to 45. i checked all fuses, and they are good. I am thinking the transfer case is screwed up. Is there an output shaft sensor that could have been screwed up by a failing transfer case bearing or something??

Could be related, especially if the vibration that you are feeling is associated with a front wheel bearing. If that's the case, the shavings could then foul the wheel speed sensor and cause ABS problems.

On the trip, we kept checking the wheels, and none appear to be warm. And I have had bad wheel bearings in vehicles before, but this vibrtes the whole drivetrain more than any wheel bearing I have experienced. I am thinking it has to do with something more integral. It was especially noticable coming down the 8% grades in Arizona into the Phoenix valley. It really seems to be the transfer case. Do you know if most GM dealers would keep such a unit handy? I'd hate to be stuck here for a week.

well, I have overheard a mech explaining this to a customer over the phone once: if engine or transmission overheats, ECM puts powertrain into a "limp mode", basically, disabling any attempts to drive vehicle extensively. in his case, there was a leaking water pump.
I am not saying it is your case... just a thought.

Yeah I know about the limp mode. I did not experience this in my situation. I was grossing about 14,000 pounds up 7% grade hills. I was holding 65 mostly in 5th gear, but it downshifted a couple times, and at about 7500 feet, it was accelerating up these mountains. Dang I love my duramax, but blame cruise control, it refused to slow down haha. I'm thinking I was low on transfer case fluid and it just got toasted because I was still hauling so much. I mean, it got all the way from Phoenix to Oklahoma and as I was leaving the mountains, the noise got worse. Finally some sensor died and now I'm stuck.

A scan is probably going to be the fastest solution to this.

It goes into the shop tomorrow hopefully. I will roll in at about opening time and see what I can get done. I will keep this thread updated.

You mention you're hauling a heavy load. I don't know your truck's specific setup (gearing/bed size,extended or crew cab), but would hazard to guess you have a long bed and 5th wheel setup...having an extended cab drops your tow rating a bit but 14k lbs appears within the truck's rating for 5th wheel use. Does the truck give you the same warning lights when it is not towing the trailer? I'm wondering if there may be a problem with the trailer brake system that is causing the truck's brakes to become overworked. If the trailer's brakes are sticking, becoming overheated or causing warpage, it may be felt in the truck as an overall vibration.

Are the wires from the controller to connector getting wet? Any water intrusion into the trailer connector? Is the trailer properly grounded to the truck? Are the trailer's brakes working properly and not worn or showing signs of being overheated? Also check the brake controller...admittedly a long shot here...the inertial electronics may be misinterpreting the steep hills as deceleration or may have been knocked out of calibration.

Just a different avenue of thought...hope this helps!

It could be something as simple as a bad u-joint. If it's the one at the rear output shaft in the transfer case where the VSS is, this could cause all sorts of issues, as the EBCM uses the VSS to determine rear wheel speed. The oscillation caused by a whopped out u-joint could cause a bad signal from the VSS to the PCM and EBCM, tripping limp-home mode as well as the brake system lights.

I thought I should update this thread while I was thinking about it. It turned out it was the transfer case, as I had initially suspected. The tailshaft broke off and it took out the rear vehicle speed sensor. That is why the gauges and anti-lock codes got thrown. A new gm transfer case and $1600 later, I fixed the problem. :)

I thought I should update this thread while I was thinking about it. It turned out it was the transfer case, as I had initially suspected. The tailshaft broke off and it took out the rear vehicle speed sensor. That is why the gauges and anti-lock codes got thrown. A new gm transfer case and $1600 later, I fixed the problem. :)

Thank for posting back how it went.

High priced fixed but if fixed all is well and good.
Good Luck with it.