Service ASR
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From: Sealy TX
St. Jude Donor 06-'07
Service ASR
I have been having the ASR light on for a while now. (96 LT4, 60K miles) Saturday, I drove about 100 miles with one stop and everuthing was OK. I made one more stop and when I started the car there was no Service ASR light, BUT, I also had no throttle, only thing I could do was idle.
I managed to get it home but I'm not sure if this is a EBTCM thing or what. I did not pick up any codes with my scanner. Ideas?
I managed to get it home but I'm not sure if this is a EBTCM thing or what. I did not pick up any codes with my scanner. Ideas?
Safety Car
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From: FL
You don't say what sort of scan tool you have but most of the inexpensive ones will only display PCM codes. The link below details a method of display using the speedometer, might be a good idea to start there. If you do have a code in memory the Factory Service Manual is invaluable for correct troubleshooting, good luck. Almost sounds like a problem with the ASR servo.
http://www.corvettebuyers.com/c4vettes/codes.htm
http://www.corvettebuyers.com/c4vettes/codes.htm
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From: Sealy TX
St. Jude Donor 06-'07
Thanks,
I don't have the scanner here but I believe it is an Auto Xray EZ Scan 1000.
I have the FSM, and was going to try the speedometer method, I just haven't had time yet.
I don't have the scanner here but I believe it is an Auto Xray EZ Scan 1000.
I have the FSM, and was going to try the speedometer method, I just haven't had time yet.
Safety Car
Joined: Jun 2006
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From: FL
Your AutoXray will definitely not display ABS codes, I have a 6000 and it will only show PCM codes. Use the speedometer to check for codes then the FSM.
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From: Sealy TX
St. Jude Donor 06-'07
I manually pulled the code with the paper clip method. In module 9.1 (ABC/TCS) I got "65", "Cable Adjuster Circuit Malfunction".
Before I pulled the code, I started the car and this time the throttle was responsive, the engine would rev up, but when I limped home the other day it would only idle since there was no throttle response, (It felt like the ASR was pushing against my foot).
I haven't started to trace it down yet. One problem of course is I don't have the "Breakout Box" required to check everything out. I unplugged the cable adjuster and checked the electrical connection and it looked good, no crud or corrosion.
I cleared the code and strated the car, no "Service ASR" light came on; but as soon as I pressed the gas pedal down, the "Service ASR and ASR Off" lights came on. I just wonder if the Throttle Position Sensor is involved in this?
Before I pulled the code, I started the car and this time the throttle was responsive, the engine would rev up, but when I limped home the other day it would only idle since there was no throttle response, (It felt like the ASR was pushing against my foot).
I haven't started to trace it down yet. One problem of course is I don't have the "Breakout Box" required to check everything out. I unplugged the cable adjuster and checked the electrical connection and it looked good, no crud or corrosion.
I cleared the code and strated the car, no "Service ASR" light came on; but as soon as I pressed the gas pedal down, the "Service ASR and ASR Off" lights came on. I just wonder if the Throttle Position Sensor is involved in this?
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Safety Car
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From: FL
From what I see looking at the diagnostic tree the TPS shouldn't be a factor. The possible causes seem to be wiring, bad adjuster assembly or EBTCM, Keep following the tree using the DVOM, good luck. I'm still betting on the adjuster.
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From: Sealy TX
St. Jude Donor 06-'07
If the Service ASR light and the ASR off lights are on, nothing happens.
If the Service lights are off, then the ASR Off will light up when you push the ASR Off button, but as soon as you press on the gas, the Service ASR lights up too.
If the Service lights are off, then the ASR Off will light up when you push the ASR Off button, but as soon as you press on the gas, the Service ASR lights up too.
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From: FL
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From: Sealy TX
St. Jude Donor 06-'07
I really don't think it's a wiring problem (frayed or corroded), the car has 60K miles, always garaged, never in the rain, no bubba work done on it.
I'll keep after it.
The real puzzle to me was that the failure caused the throttle to not operate. I could push on it and it was like it had been disconnected (except there was a lot of resistance on the pedal). Then a couple of days later, I start the car and no pedal resistance and it will rev up.
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From: Mexico Beach FL
Just a guess here:
The ASR has to "learn" the TPS (Throttle Position Senser) output.
The ONLY way I know to accomplish this is with the Vetronix scan-tool.
But, then, if you had the Vetronix scan-tool, you would be able to run diagnostics on the entire ABS/ASR system.
There is a TPS buffer down beside the windshield washer reservoir -- it looks like a black box plugged in.
The only purpose of the TPS buffer is to isolate the TPS signal and feed it to the ASR.
You might try to unplug the TPS buffer and plug it back in to see if it reseats.
In addition, you may have a bad rear wheel speed sensor.
Tom Piper
The ASR has to "learn" the TPS (Throttle Position Senser) output.
The ONLY way I know to accomplish this is with the Vetronix scan-tool.
But, then, if you had the Vetronix scan-tool, you would be able to run diagnostics on the entire ABS/ASR system.
There is a TPS buffer down beside the windshield washer reservoir -- it looks like a black box plugged in.
The only purpose of the TPS buffer is to isolate the TPS signal and feed it to the ASR.
You might try to unplug the TPS buffer and plug it back in to see if it reseats.
In addition, you may have a bad rear wheel speed sensor.
Tom Piper
Last edited by Tom Piper; Oct 24, 2007 at 12:33 PM.
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From: FL
Definitely, I've got enough extra parts now!
I really don't think it's a wiring problem (frayed or corroded), the car has 60K miles, always garaged, never in the rain, no bubba work done on it.
I'll keep after it.
The real puzzle to me was that the failure caused the throttle to not operate. I could push on it and it was like it had been disconnected (except there was a lot of resistance on the pedal). Then a couple of days later, I start the car and no pedal resistance and it will rev up.
I really don't think it's a wiring problem (frayed or corroded), the car has 60K miles, always garaged, never in the rain, no bubba work done on it.
I'll keep after it.
The real puzzle to me was that the failure caused the throttle to not operate. I could push on it and it was like it had been disconnected (except there was a lot of resistance on the pedal). Then a couple of days later, I start the car and no pedal resistance and it will rev up.
http://cgi.ebay.com/ebaymotors/1994-...spagenameZWDVW
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From: Mexico Beach FL
....The real puzzle to me was that the failure caused the throttle to not operate. I could push on it and it was like it had been disconnected (except there was a lot of resistance on the pedal). Then a couple of days later, I start the car and no pedal resistance and it will rev up.
The ASR functions by:
1) Relaxing the throttle to limit horsepower.
2) Retarding the timing to limit horsepower.
3) Applying one or more rear brakes to limit wheelspin.
The computer senses Yaw, speed, engine rpm, etc to determine which of the above it will use.
In your case, it sounds like it is relaxing the throttle a lot.
Does the problem go away when you turn off ASR completely?
Tom Piper
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From: Sealy TX
St. Jude Donor 06-'07
Good thinking! This might be worth watching if you determine it is the cause.
http://cgi.ebay.com/ebaymotors/1994-...spagenameZWDVW
http://cgi.ebay.com/ebaymotors/1994-...spagenameZWDVW
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Joined: May 2004
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From: Sealy TX
St. Jude Donor 06-'07
Safety Car
Joined: Feb 1999
Posts: 3,504
Likes: 4
From: Mexico Beach FL
I say that because the ASR should not attempt to relax the throttle when turned off.
It can't be the TPS buffer since it is turned off.
What happens if you disconnect the electrical connector for the relaxer/servo by the master cylinder?
When you do this, ignore any Service ASR lights since that would be normal with the relaxer not connected.
Does the problem go away?
Tom Piper