DBW going into limp mode
05-30-2015, 07:55 AM
#1
DBW going into limp mode I've got an 02 escalade LQ9 in my 68 corvette with a Richmond 6 speed. Stock tune, ecu, TAC, and pedal.
It occasionally loses the DBW throttle (limp mode, just idles), usually just getting into the throttle when accelerating from a stop. Shutting it off and disconnecting the battery resets everything and it will work fine. It also never gives me a check engine light.
I noticed it usually occurs after I get the car out of storage and seems to be in the same throttle position, so I assumed it was a dead spot or corrosion in one of the pedal position sensor potentiometers. I replaced the APPS but it still occasionally occurs. The TAC is also new. Wiring and connectors look good.
I've never been able to check the ecu for readings on the pedal sensor since I've never had it occur in my driveway.
My next step is the TPS but thought that would give a CEL.
Any other thoughts?
It occasionally loses the DBW throttle (limp mode, just idles), usually just getting into the throttle when accelerating from a stop. Shutting it off and disconnecting the battery resets everything and it will work fine. It also never gives me a check engine light.
I noticed it usually occurs after I get the car out of storage and seems to be in the same throttle position, so I assumed it was a dead spot or corrosion in one of the pedal position sensor potentiometers. I replaced the APPS but it still occasionally occurs. The TAC is also new. Wiring and connectors look good.
I've never been able to check the ecu for readings on the pedal sensor since I've never had it occur in my driveway.
My next step is the TPS but thought that would give a CEL.
Any other thoughts?
05-30-2015, 08:49 AM
#2
Dbw When I was tracking down my problem I found a video on the 'net that discribed your symptoms, random and when under a load. In that case (and others) the problem was one wire going to the throttle body was loose. Very hard to detect and somewhat common. Guess they had some bad crimps on just the one wire and only held in by a couple of strands. Under load the wire is unable to keep up, causing a mismatch signal and limp mode. My scanner is able to read the "U" codes which is where something like that will show up. Best bet is to search the net and the video will tell all.
05-30-2015, 09:27 AM
#3
TECH Regular
There was a bulletin about the throttle body wiring being broken inside the insulation about an inch from the throttle body. If I recall its almost always the yellow wire. Yours may be something different though. What MAF do you have?
05-30-2015, 09:27 AM
#4
Pedal I have also replaced the pigtail before but the only thing that fixed it permanently, was to go to the dealership and have the computer reflashed. I tried to change some things in my dads transmission settings with hp tuners and that crap with the gas pedal started. After exhausting all other resources, I had it reflashed at the dealership and it never happened again. Good Luck.
06-06-2015, 03:59 PM
#6
Update......
Wiring checked out OK.
But I noticed the throttle response seemed a bit sluggish before it went into limp mode. I decided to pick up a used TB with motor and TPS. It was about the same price as a new TPS. The used one was really gunked up on both sides with carbon, oil, etc, so I cleaned it up and went to put it on.
This is what the old TB looked like inside. I'm guessing the excessive buildup was causing a delay in opening off throttle resulting in an error and limp mode. I actually read about the same issue somewhere years ago. New/used one is bolted on and runs great. Now I guess I've got a spare to clean up.
Wiring checked out OK.
But I noticed the throttle response seemed a bit sluggish before it went into limp mode. I decided to pick up a used TB with motor and TPS. It was about the same price as a new TPS. The used one was really gunked up on both sides with carbon, oil, etc, so I cleaned it up and went to put it on.
This is what the old TB looked like inside. I'm guessing the excessive buildup was causing a delay in opening off throttle resulting in an error and limp mode. I actually read about the same issue somewhere years ago. New/used one is bolted on and runs great. Now I guess I've got a spare to clean up.
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06-09-2015, 09:14 AM
#9
aknovaman,
The pedal and TAC are correct for the vehicle (02 escalade, LQ9). The car ran great for 5 years as is. The intermittent pedal control loss just started, it also is getting more common.
I replaced the pedal APPS thinking that was the issue, but still have the intermittent problem. Also did the TB cleaning and relearn. TAC was new in 2010.
I contacted the tuner for details on the file. I don't have hp tuners, etc, but it seems disconnecting the pedal should throw a code.
The pedal and TAC are correct for the vehicle (02 escalade, LQ9). The car ran great for 5 years as is. The intermittent pedal control loss just started, it also is getting more common.
I replaced the pedal APPS thinking that was the issue, but still have the intermittent problem. Also did the TB cleaning and relearn. TAC was new in 2010.
I contacted the tuner for details on the file. I don't have hp tuners, etc, but it seems disconnecting the pedal should throw a code.
