Bad start to road trip!

[hertahoe]

So got the oil changed earlier in the week at dealership (free lifetime oil changes), had dealership rotate tires and I put on new wipers. No running issues since last April on another volleyball road trip when my transfer case had issues and an ignition coil. So about two hours into a 5 hour trip, crap went crazy. Doing 60mph, slowed down to around 30 for traffic and started to accelerate and ABS and brake light came on and would not shift out of gear. Speedo was bouncing between 30-50 and I could get it to 40mph with rpm's around 4k. Got over to outside lane and took exit. Drove about a mile at 35 to get into decent area to park. Turned off, restarted fine, but lights still on. Didn't have my code reader. I had to get to destination for my daughter and her friend. So found a rental car agency about a mile away. Drove to it, rented car, left Tahoe in lot and drove to Eugene. So now I'm looking for the exerts to try to trouble shoot what the hell is going on. I will try to respond when I can, but will be attending volleyball games all day long until Monday night! My plan is to drive back to Washington on Monday night, then drive back down Tuesday morning to take it to shop or fix if I don't need to remove engine Much appreciate all the input!

 

[iamdub]

We'd have to write books to suggest all that could be wrong. First step is to get a scanner on it. If even to drive it to a nearby parts store to borrow one. My concern with that is if it's intermittent and the fault(s) have cleared, the codes could go away during the drive to the parts store and you'd be left in the dark until the problem returned.

Guesses off the top of my head- failed sensor or related circuitry telling the PCM erroneous info and it responding to it as programmed. Bad MAF, MAP, TPS, VSS, etc. Something that provides the PCM with vital info has thrown it for a loop with info that doesn't fit. Or the circuitry in between has cut power and/or coms between the PCM and sensor.

If multiple sensors and/or systems failed at once, see what they all have in common. This is usually a ground. Are there any other seemingly small oddities that have occurred prior to this that you haven't mentioned?

 

[hertahoe]

We'd have to write books to suggest all that could be wrong. First step is to get a scanner on it. If even to drive it to a nearby parts store to borrow one. My concern with that is if it's intermittent and the fault(s) have cleared, the codes could go away during the drive to the parts store and you'd be left in the dark until the problem returned.

Guesses off the top of my head- failed sensor or related circuitry telling the PCM erroneous info and it responding to it as programmed. Bad MAF, MAP, TPS, VSS, etc. Something that provides the PCM with vital info has thrown it for a loop with info that doesn't fit. Or the circuitry in between has cut power and/or coms between the PCM and sensor.

If multiple sensors and/or systems failed at once, see what they all have in common. This is usually a ground. Are there any other seemingly small oddities that have occurred prior to this that you haven't mentioned?

Much appreciated. I know at this point it's throwing mud on the wall without a scan.

 

[swathdiver]

Do your best to enjoy the time with the kids and then get after your plan.

 

[nonickatall]

So got the oil changed earlier in the week at dealership (free lifetime oil changes), had dealership rotate tires and I put on new wipers. No running issues since last April on another volleyball road trip when my transfer case had issues and an ignition coil. So about two hours into a 5 hour trip, crap went crazy. Doing 60mph, slowed down to around 30 for traffic and started to accelerate and ABS and brake light came on and would not shift out of gear. Speedo was bouncing between 30-50 and I could get it to 40mph with rpm's around 4k. Got over to outside lane and took exit. Drove about a mile at 35 to get into decent area to park. Turned off, restarted fine, but lights still on. Didn't have my code reader. I had to get to destination for my daughter and her friend. So found a rental car agency about a mile away. Drove to it, rented car, left Tahoe in lot and drove to Eugene. So now I'm looking for the exerts to try to trouble shoot what the hell is going on. I will try to respond when I can, but will be attending volleyball games all day long until Monday night! My plan is to drive back to Washington on Monday night, then drive back down Tuesday morning to take it to shop or fix if I don't need to remove engine Much appreciate all the input!

Sounds to me like an ABS Sensor failure. I don't know how GM made that at the Tahoe, but I know that from many German cars that the speed signal comes from one ABS sensor, mostly the one in front on the right side.
If this sensor makes trouble, you probably have a bouncing Speedo and you have no acceleration because your ECM and you transmission control need that Signal.
I think it was the failure of a sensor, because when you shut down the engine and start again and everything runs fine, looks very much like that.
Normalwise ABS Sensor failure are security related, so it stays in memory and your ABS light stays in.
But it's only a suggestion

 

[ScottyBoy]

Not sure a

Sounds to me like an ABS Sensor failure. I don't know how GM made that at the Tahoe, but I know that from many German cars that the speed signal comes from one ABS sensor, mostly the one in front on the right side.
If this sensor makes trouble, you probably have a bouncing Speedo and you have no acceleration because your ECM and you transmission control need that Signal.
I think it was the failure of a sensor, because when you shut down the engine and start again and everything runs fine, looks very much like that.
Normalwise ABS Sensor failure are security related, so it stays in memory and your ABS light stays in.
But it's only a suggestion

That does sound plausible. I know when you have a bad ABS sensor, it can mess with the speedo, trigger an ABS light, Traction Control light, and even a "Service 4wd" error message if you have 4wd.
I've never heard of the transmission not wanting to shift though, but I guess it's possible. If it does turn out to be bad ABS sensors in the front wheels, I strongly suggest you just replace the entire wheel bearing/hub assembly. It's easier to change the entire assembly, as the hub assembly needs to be removed anyway to replace the ABS sensor, the ABS sensor is included when you buy a new hub assembly, plus the cost of an entire hub is not too much more than a bare ABS sensor. Let just hope it's something as simple as an ABS sensor and not a transmission issue.

 

[hertahoe]

Well, drove down to Portland to return rental and get Tahoe to shop. Scanned it and abs control module...Nice little indy shop and guy was great. He scanned it multiple times and cleared codes. I would take it around the block to see if lights came back on and they did. Apparently there was no info coming from sensors. He believes it's a bad abs control module. Basically ran out of time and I ended up getting a hotel nearby. Drove car to hotel at 35mph max. He is going to run tests on the circuits before putting in new module to make sure its bad. At first look over, he saw the plug to the module barely connected. Secured it back to plug, but didn't solve issue. But it is a costly part! Hope it solves the issue so I can get back to family!

PS - daughter is the starting libero for a U16 national team in our home town. First year the girls are together and they took 26th in the gold bracket outta 150 teams.

 

[nonickatall]

Possible is it possible to remove

Well, drove down to Portland to return rental and get Tahoe to shop. Scanned it and abs control module...Nice little indy shop and guy was great. He scanned it multiple times and cleared codes. I would take it around the block to see if lights came back on and they did. Apparently there was no info coming from sensors. He believes it's a bad abs control module. Basically ran out of time and I ended up getting a hotel nearby. Drove car to hotel at 35mph max. He is going to run tests on the circuits before putting in new module to make sure its bad. At first look over, he saw the plug to the module barely connected. Secured it back to plug, but didn't solve issue. But it is a costly part! Hope it solves the issue so I can get back to family!

PS - daughter is the starting libero for a U16 national team in our home town. First year the girls are together and they took 26th in the gold bracket outta 150 teams.

I don't know the specific control unit, is it possible to remove the circuit board separately? If so, I would try the following.

I would remove the circuit board and bake it in the oven for an hour at 230° Fahrenheit.

That sounds strange at first, but it often helps to repair circuit boards, because it is often the cold solder joints on the circuit boards that cause the errors. At 230°, the solder becomes soft again, reconnects and you can save a lot.

I recently got an expensive engine control unit from a classic car, that is no longer available is repaired in this way. Your control unit can't get any more broken. Otherwise I would also consider installing a used one.

 

[hertahoe]

Owner of shop happen to stop by. He suggested taking out module and take it apart. All the torx screws are rusted, so they have to take the whole ABS unit off, which means bleeding the system. The Tahoe has almost no rust, but always in the wrong spot at wrong time.

 

[hertahoe]

More bad news. Module put in, brakes bled, but ABS light came back on and speedo still bouncing. Truck can go over 40mph though. They think when the transfer case was replaced (4/22) that the shop didn't calibrate it to truck. If I drive it, more than likely, it will burn up new module. Another interesting issue. Scan keeps saying there is a speed sensor on the rear wheel but there is none. Only speed sensor is on top of transfer case. Now I'm getting concerned and pissed for the amount of time I am wasting. Looks like another night spent in hotel. FML