ABS code 25, thing has me stumped
Thread Starter
Race Director
Joined: Jan 2008
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From: oregon
ABS code 25, thing has me stumped
Well here it is, i'm new to the vette world and previously have been in honda land. I received a pretty good deal on a 90 6spd car that put 352hp to the wheels on a dynojet. On to my question, i have this service abs light that flashes a code 25. googled it and found it to be a left front abs sensor. replaced that and i still have the light. any ideas, thoughts? Any help would be much appreciated 
Other than that the car is fun, well except the rear spring rates are way too soft and the car will swing around in front of you way too easy.
Other than that the car is fun, well except the rear spring rates are way too soft and the car will swing around in front of you way too easy.
Thread Starter
Race Director
Joined: Jan 2008
Posts: 16,028
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From: oregon
using one of those 30 dollar boxes you plug in under the dash and count the abs flashes. tonight i cleared it, drove, ran it again and now get code 32 and 36. basically 3 of 4 corners of the car have issues? do these things have a central computer that runs abs or some place that commonly comes loose? it's beyond unlikely that so many sensors would die all at once.
Drifting
Joined: Apr 2007
Posts: 1,339
Likes: 2
From: port charlotte fl
I know more about my '87 than your '90 but i thought they were similar when it comes to codes.I wasn't aware you could read abs codes.Are you sure those aren't engine codes you are seeing?Yes the abs system has it's own computer.
Thread Starter
Race Director
Joined: Jan 2008
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From: oregon
From what i can find the ability to read abs codes began in 1990 when they updated to the Bosch s2 abs computer. On a GM code reader that basically is a paperclip with a switch; you can set it for ecu or abs. The difference is which pins it shorts. I'm going to check all of my connections today and see what i can find. My real clue is with the fact all these codes came on at once. 3 sensors don't go all at once, that has me thinking computer. I was just wondering if any 1990-1991 people have experienced similar. In 1992 ASR came about and yet more changes happened. Well off i go, fuses and grounds are the first places i'm going to look. Oh did i mention this came on after some serious sideways driving? Car was getting the hell beat out of it. 6500rpm shifts, drifts etc..Vibrations issues ever been known to cause anything?
Drifting
Joined: Apr 2007
Posts: 1,339
Likes: 2
From: port charlotte fl
The only thing I can suggest is to pull all the sensors and clean them and the magnetic senders.Probably covered in brake dust and rubber.Try disconnecting the battery afterwards and see if it clears the codes.
Le Mans Master
Joined: Apr 2002
Posts: 5,726
Likes: 46
From: Waukesha WI
St. Jude Donor '15
The EBCM (Electronic Brake Control Module) is located in the storage compartment in the cargo area behind the driver's seat. You can check to see if maybe the connector popped loose. Its ground comes from right above the oil filter - another possible problem.
There are diagnostic charts in the FSM that would answer many of your questions. If you plan to keep the car or wrench on it yourself, it would be advisable to pick one up. It will make the nightmare of electronics on these cars far more manageable.
There are diagnostic charts in the FSM that would answer many of your questions. If you plan to keep the car or wrench on it yourself, it would be advisable to pick one up. It will make the nightmare of electronics on these cars far more manageable.
Thread Starter
Race Director
Joined: Jan 2008
Posts: 16,028
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From: oregon
going to check this out tomorrow at the latest. The ground you speak of sounds likely. This is not the stock motor and i wouldn't be suprised if a loose ground was the problem. Sometimes the abs light comes on quickly, sometimes it takes 5-10 minutes of driving. Always code 25,32,36. Your suggestion is very helpful as you took me in a direction i would have never went without your advice.
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Thread Starter
Race Director
Joined: Jan 2008
Posts: 16,028
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From: oregon
I also forgot to mention that there is no abs even when the service light is not on. like say for example, i fire the car, drive 2 min, pound the brakes, i have no abs. The light will follow 3 minutes later or so but not at first. Also i've had weird brake light things, like brake lights come on when i turn the car off. Now from what i can tell the abs shares a fuse with the brakes...any ideas so far...i'm going to do the above mentioned in the AM
Thread Starter
Race Director
Joined: Jan 2008
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From: oregon
Ground checks out, my pump is not making the whurrr noise that it is supose to. checking the bosch motor relay now, at least trying to. do these pumps fail very often? Normally these suckers last the life of a car.
Thread Starter
Race Director
Joined: Jan 2008
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From: oregon
Okay, hopefully someone knows an answer to this question. 
see this relay? This is the motor pump relay. Another one is before it which checks out, this one sits on top of your abs motor. The problem is, it's not clicking. When i push the relay with a screwdriver and make the tab contact my motor fires right up. I'm getting closer and closer to being sure this is my problem, i just have never had to replace a relay like this before. No signs of anything being burnt. How exactly do these work? Magnetic pick up? Current? Is it possible it could fail with no visable cause?
see this relay? This is the motor pump relay. Another one is before it which checks out, this one sits on top of your abs motor. The problem is, it's not clicking. When i push the relay with a screwdriver and make the tab contact my motor fires right up. I'm getting closer and closer to being sure this is my problem, i just have never had to replace a relay like this before. No signs of anything being burnt. How exactly do these work? Magnetic pick up? Current? Is it possible it could fail with no visable cause?
Drifting
Joined: Apr 2007
Posts: 1,339
Likes: 2
From: port charlotte fl
It's an induction coil.You apply a charge to it which energises the coil creating an electromagnet which sucks in the central core and closes the contacts which allows the electrical flow to operate whatever system it's connected to.There are tons of them on a Vette and yes they can fail but worst still they can become intermittent.That's the bitch. I've seen this on the VATS circuit,the fans and the starter.My last f*#! up was with the MAF burn off relay.I have a Howell service manual which allows me to quickly find the causes of my codes and fix them but yours is obviously different having the ABS codes but the relays can still cause the same problems.If the recipient works when you physically close the points the relay has failed.
Le Mans Master
Joined: Apr 2002
Posts: 5,726
Likes: 46
From: Waukesha WI
St. Jude Donor '15
Yes, it is possible for the relay to fail w/ no external signs. I've lost a few on my 90 this way. Before replacing it, I would run the car with a multimeter hooked up to the relay contacts and be sure the control unit is requesting the relay be engaged - if it is, then you may have found the problem. If not, then you'll have to look elsewhere.
You only need to run the car up to 3-5mph (forward or reverse) to get the ABS self-diagnostic to run - it will run the motor and valve body. There is no need to try locking the brakes.
The good news is those relays are pretty cheap and readily available - you may have to ask the parts counter for it by a different name, tho.
You only need to run the car up to 3-5mph (forward or reverse) to get the ABS self-diagnostic to run - it will run the motor and valve body. There is no need to try locking the brakes.
The good news is those relays are pretty cheap and readily available - you may have to ask the parts counter for it by a different name, tho.
Thread Starter
Race Director
Joined: Jan 2008
Posts: 16,028
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From: oregon
That's the odd part, i would have no abs and no service abs light at first. Sometimes the codes would trip, sometimes it took a few minutes. I did one test with power on pin 87 {this has voltage on the abs pump when the car is on} then ground the other 3 pins one at a time. relay would not fire. If this isn't the issue then what sends signal to it is. I know my abs pump is good which leaves only the abs computer. The other 2 relays are good.
