My ABS, SLIP, TCS and BRAKE light had been turning on intermittently for the past week. Yesterday, the lights turned on full time, and the electric pump in my ABS control unit is now running full time even when the car is off and keys out of the ignition. I didn't want to drain my battery, so I unplugged the wiring harness next to the ABS control unit (located in the same bay as the brake fluid reservoir). Now, my Service Engine Light is on too.

The car seems to run fine. I've done a few aggressive stops (55mph-->0) to make sure I don't have a rear wheel locking/brake balance problem. But, it's hard to tell how it will behave from 110 to 30.

Also, my speedo and cruise control doesn't work (not surprising), and I'm no longer 'logging' in miles on the odo.

I have a track day this Friday, and I'm not sure if I'll get this resolved by then. Have any of you guys driving on the track with this harness unhooked? I've done my search, and I know some of you have disconnected the yaw sensors and/or added a cutoff switch for the wire located under the hazard button.

 

You did check your brake fluid level right?

Are You really planning on going to the track with all those lights on and no speedo?

Chris

 

I sure did check the brake fluid level. My only concern with driving on the track with all these warning lights on are ABS and EBD, and whether the car relies on this system to brake efficiently. I've fixed the premature ABS intervention by going with a lower friction brake compound in the rear, so I might be okay.

As for the speedo, I don't even look at that gauge on the track. I used the tach, and check the temp and pressure gauges, but the speedo is not important.

Regardless, I'll be taking precautions on my first couple sessions, and give myself plenty of braking distance....

 

I would pick up a cheap OBDII reader and get the code on that engine light. You're probably right to assume that it is related to the computer gremlins, but there is a chance that it's an unrelated engine code that should be addressed.

While I can appreciate you trying to tackle things yourself, it might be time to bite the bullet and bring her into a shop. Especially before a track day. Your secret would be safe with us even though you're a highly educated engineer.

 

autozone check the light for free. likely to be a wheel speed sensor. explains your speedo and abs light. just a thought

 

Thanks Dave, I'll pick up one of those readers, and run through some diagnostics. I have a really sick feeling that I'm going to have to plunk down $1500 for a new ABS control unit. Those things look heavy and expensive!!!

Hiring someone to fix my car is like picking up a fat and nasty hooker when I have an attractive wife at home. Oh well, I guess we could all use some variety...

 

yea those lights came on on my audi a while back. at high speeds i couldnt tell but when i slammed on the brakes from like 15 the wheels would lock up. dont know if that helps other than all those same lights came on on my audi. that sucker was 2400 bux!

 

http://www.automotiveforums.com/vbulletin/t94611.html

The internet is simply awesome.

 

your problem could be a lot of things.... module, wheel sensor, tone wheel, wiring....until you get that code read, we can't help.

go get it read!!!

peer pressure should do the trick! autozone as I mentioned before will pull the code no charge...i think.

 

I had the same issue on my Z last year but it's probably a different cause.
In my case I had worn the front pads to the backing plates on the track and scored one rotor. This was at the last session of the weekend. I just put in new pads and drove home. I figured I would replace the rotors once home. The differential in braking force from right (not scored) to left (scored) is what caused the ABS unit to go bezerk. Notice I say bezerk and not fail... Once I changed the rotors and pads and did some driving around, the problem went away. I had talked to the dealer and they had called the Nissan hotline or whatever they call it and they confirmed that difference in friction was most likely causing the problem. What is the condition of your brakes ?

Hope you get your issue resolved.

On a slightly different note, I replaced an ABS module on an Audi A4. I had the electronics portion shipped to Gavin Curtis At Circuit Solutions and he fixed it for much less than a new one. That may be an option for you.

 

I've seen this on a few cars (mostly BMW) and in those cases it was a bad wheel speed sensor - reading on one was waaaaaaay of, like 8ohm, 8ohm 8ohm, hmm why is this one 2.6Mohm

 

Two days before your track event..

Have you placed your order at Hertz for the 'track' rental car?

 

Unfortunately no. I did several threshold brake tests from 70 to 0, and it behaved. I'm going to do a few more tonight on a deserted road with wide shoulders, and try to lock things up.

If it doesn't feel right, I'm simply going to forfeit my day with T.E.A.M. Maybe they'll give me partial credit for a future event.

If I can lock my front up before the rear, I'm still going to drive tomorrow...just baby the car during the first session, and decide whether to do the rest of the day, or pack up, and go back home.

I'm going to send Gavin the module for repair. He stated the symptoms (ABS pump runs while engine off) indicates a short in the EBCM, which he can repair for $150-$200

 

for the love of all things mechanical...please tell me you had someone pull the code already. i mean we have been through this all week right??? GET A CODE READER!!!!!!!

FREE CHECK AT AUTOZONE.

feel like i am talking to a wall here...not trying to be an *** but we all keep saying to do this and that, what have you actually done to DIAGNOSE the codes!??!??!!?

 

I did not get a code read because I've already determined that there is a short in the EBCM. I've diagnosed bad speed sensors (in other cars) before, so I know those symptoms. I know this problem is not caused by bad speed sensors. This problem is different, and I am convinced it is a short in the module.

Don't you worry, I'll get those codes read tonight at Autozone.

 

cool, hope your right. good luck with it. always other track days... better safe then sorry.

 

Got the codes. Had to plug the ABS control harness back in.

P0500 Malfunctioned speed sensor
P1212 Malfunctioned Fuel air meter
P0460 Fuel Level sensor
U1001 Manufacturer specific DTC

I did 6 sessions yesterday. I babied the car for the first session, but experimented with hard braking at the end of the front straights. When the brakes were applied hard enough, only one front tire would lock up.

Once, the rear locked up, and I suspect it was due to a poor heel toe downshift. I decided to give myself just a little more braking room and work on smoothness, and didn't get any lockup in the last 4 sessions of the day.

Lessons learned.
1) Without EBD/ABS, you need to be very smooth, so I learned that I could be smoother at braking.

2) If and when I lock up, it's like sliding over ice. It will make the hair on the back of your neck stand, QUICK!

3) EBD/ABS is our friend...For some reason, I expected both wheels to lock up when braking in a straight line. That wasn't the case. I think EBD would have alleviated that. As for ABS (when functioning normally), I rarely had it intrude once I selected the right brake pads. But, it's good to have it around when doing some very late braking. I couldn't do any late braking or trail braking yesterday, it wasn't worth risking it.

I removed the ABS module and pump. Attached is a photo of the EBCM that I removed from the pump unit. It took about an hour to disassemble, and I'm a slow worker.

 

so the harness was just unplugged???????

Glad to see you had fun and kept the car together. "Smooth is fast"

 

Yes, I just drove with the harness unplugged. The harness uses a locked lever. You just press the grey tab, then lift the lever to unlock the harness from the EBCM. It's really easy to get to, especially if you just remove the plastic shrouding around the drivers side compartment.

Come to think of it, before ABS was invented, all the racers had to drive their vehicles like I was doing yesterday. It takes a lot of getting used to, and I certainly felt like I didn't have a safety net to fall back on. I was over 3 seconds slower around the track yesterday...

 

oh i thought you meant the module was unplugged.

check out a VSS for the problem.