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Post by LAurora on Feb 10, 2014 18:39:33 GMT -6
This is a rather long post, but it has lots of info because I have been troubleshooting for a while and am just lost now.
I have a 2001 4.0l Aurora with 193k miles, I bought it with 118k 7 years ago. For the past two months, the ABS and Trac Off light would sporadically turn on and off with no discernible pattern. About a week ago the ABS and Trac Off light came on, and have stayed on everytime I have turned the car on. At the same time, I noticed that the brake pedal was not as stiff as usual. It would be behave what I thought to be normal until about half way down, and then with constant pressure, it would just mush down the rest of the way. Thinking there was a leak, I checked all of the lines and was unable to find a leak. I then bled the lines and did not get any air bubbles. Additionally, there was no fluid loss occurring from the reserve. Given that the brake master cylinder appeared to be the original, I replaced the master cylinder. I bench bled the master cylinder, and rebled the brake lines. Again, no bubbles and no fluid loss. I expected this to fix the problem but it did not. I still have mushy brakes, and I still have an ABS and Trac Off light on constantly. The thing is, it doesn't drive like there is a loss of fluid. I haven't had to put any fluid in since I replaced the master cylinder. I can drive it around on the streets and it behaves almost like normal. If I try to go above 40 and hit the brakes hard, that's where the performance difference appears. At that point, its very obvious that the brakes aren't performing up to expectations, and my foot is at the floor before the car stops properly.
Not sure what to do, I purchased the Palmer Performance ScanXL Standard, and GM Enhanced diagnostics software/hardware to pull the advanced OBD codes. Below is the list of codes that popped.
P1571 Traction Control Torque Request Circuit U1040 Lost Communications with Brake/Traction Control System C1221 Left Front Wheel Speed Sensor Input Signal = 0 C1222 Right Front Wheel Speed Sensor Input Signal = 0 C1223 Left Rear Wheel Speed Sensor Input Signal = 0 C1224 Right Rear Wheel Speed Sensor Input Signal = 0 C1234 Left Rear Wheel Speed Sensor Circuit Open or Shorted C1235 Right Rear Wheel Speed Sensor Circuit Open or Shorted C1238 Brake Thermal Model Exceeded C1241 Variable Effort Steering Circuit Malfunction C1242 Pump Motor Circuit Open C1243 Pump Motor Stalled C1248 DRP Disabled C1254 Abnormal Shutdown Detected C1277 Requested Torque Signal Circuit Malfunction C1282 Yaw Rate Sensor Bias Circuit Malfunction C1283 Excessive Time to Center Steering C1287 Steering Sensor Rate Malfunction C1288 Steering Sensor Circuit Malfunction C1295 Brake Lamp Switch Circuit Open C1298 PCM Class 2 Serial Data Link Malfunction U1255 Loss of Class 2 Communication
Now granted, it could have had some of these codes before and I just wasn't able to read them with the basic OBD reader I had, but that's a lot of codes!
Given the number of codes, I don't know where to even begin. What am I missing here? Any recommended next steps? I'm about ready to light the aurora on fire and dance naked around my offering to the car gods.
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Post by awehlage on Feb 10, 2014 20:38:05 GMT -6
Has the "serv stability sys" message appeared on the DIC. More like than not you have a bad wheel speed sensor which is making the car illuminate the ABS light and TRAC OFF light on the dash. The manual says to turn the car off and turn back on to see if the lights go off. If they stay on line you are saying on every startup its time to start diagnosing.
Sent from my XT901 using proboards
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tigger
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Post by tigger on Feb 10, 2014 21:49:27 GMT -6
Sounds like failed ABS Control Module.
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Post by LAurora on Feb 10, 2014 21:55:54 GMT -6
The DIC hasn't worked in ages, so I don't know if the "serv stability sys" message is on. Would you get a DTC code with that?
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Post by LAurora on Feb 10, 2014 23:24:39 GMT -6
tigger, Is there anyway to check the ABS Control Module? Or do I just have to send it to Module Masters and Hope for the best...
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Paulaurora
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Post by Paulaurora on Feb 11, 2014 13:20:02 GMT -6
I would erase all the codes and see which once will appear back.Most likely its your hub bearings or the abs wires are no good.
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Post by awehlage on Feb 11, 2014 21:17:29 GMT -6
The DIC hasn't worked in ages, so I don't know if the "serv stability sys" message is on. Would you get a DTC code with that? I did not have any DTC codes set when my TRAC OFF, ABS, and SERV STABILITY SYS all came on at the same time. Also make sure all the wheel speed sensors are connected and maybe clean them with some electrical parts cleaner and pack them with dielectric grease. There is a procedure to check the resistance of each rotor. You have to hook up a DMM, spin the rotor, take a reading and compare it to the FSM specs. If its out of line you should replace the wheel sensor. Sent from my XT901 using proboards
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Post by LAurora on Feb 12, 2014 0:58:25 GMT -6
Progress has been made! But I'm still having problems...
Short Version: I only have 4 ABS codes now. C1242 Pump Motor Circuit Open C1243 Pump Motor Stalled C1287 Steering Sensor Rate Malfunction C1288 Steering Sensor Circuit Malfunction
Long Version: I cleared the DTC codes before beginning to work on it today. I disconnected the two EBCM connectors, as well as the main wiring harness connector, sprayed them down with electronics cleaner and reconnected them. I disconnected the Wheel Speed Sensors, sprayed them with electronics cleaner and reconnected them. I checked the wires from the WSS to the EBCM, and the EBCM connector to the main harness and was unable to find any damage/breaks. All of the wiring still had the protective sheathing on it, and did not seem to have any damage.
The only wiring that was out of place were two wires that the previous owner had added to the harness. They cut a white and a brown wire from the main wiring harness connector, and ran two wires to the the EBCM connector where they connected them to a white and brown wire again. They have been like that since I first got the car 7 years ago, and I checked the soldered connections so I don't believe that is the problem.
I am somewhat concerned because I was not able to find a ground strap. I thought that this module had a ground strap that connects the EBCM to the frame, but I didn't find it. So either, I didn't look hard enough, or it doesn't have one. I found the big main connection that is on the side of the EBCM, and the smaller connection with two wires that goes underneath the EBCM.
It seems like the two possibilities are: 1) I missed the ground strap and its messing with the EBCM 2)the BPMV went bad and I need a new one.
Any thoughts/suggestions?
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Paulaurora
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Post by Paulaurora on Feb 12, 2014 12:06:45 GMT -6
The last 2 is not ABS codes its for steering wheel position sensor.
first 2
C1242 - Pump Motor Circuit Open C1243 - BPMV Pump Motor Stalled
The pump motor your codes refer to is part of the anti-lock brake and traction control unit located at the bottom LF corner of the engine cradle. You can't miss it; all the brake plumbing on the vehicle passes through this module.
And that pump motor has a chassis ground wire that exits the motor case and is bolted to an adjacent chassis hole. That chassis connection can rust/oxidize. Remove the bolt and apply a dose of wire brush and use star washers on both sides of the terminal when reassembling.
A broken chassis ground wire would also be a possibilty.
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bobsblue95
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Post by bobsblue95 on Feb 12, 2014 12:33:39 GMT -6
Based on the original laundry list of codes, my thoughts are bad controller module or bad ground to the controller. Sounds like you're on the right track. Simple enough to try grounding it and test again.
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Paulaurora
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Post by Paulaurora on Feb 12, 2014 14:40:38 GMT -6
Short in the wiring or bad battery/alternator can cause issues as well.
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bobsblue95
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Post by bobsblue95 on Feb 12, 2014 14:44:54 GMT -6
Short in the wiring or bad battery/alternator can cause issues as well. True, but it probably wouldn't be isolated to the ABS. There would be random engine codes too.
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Post by LAurora on Feb 16, 2014 19:06:21 GMT -6
So it took me a couple days, but I got back under the car. I double checked, and was unable to find a ground strap. The only wires that I found were the BPMV electrical connector that runs from the pump motor, underneath the whole box and goes into the EBCM, and the EBCM connector that goes back to the main wiring harness. I also checked my factory service manual for replacing the EBCM and the BPMV and it says nothing about a ground strap. It only says to disconnect the two cables that I mentioned earlier. I can't find a ground strap or connector on my car, nor can I find one in any of the diagrams that I looked through. Am I missing something here? Should I upload pics to show what I have ?
Paulaurora, I know its asking a bit much, but could you check on your aurora for a ground strap? I have the same model, and I can't find one.
I'm wondering if I should pull the whole thing out and check the pump and pump connector...
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Paulaurora
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Post by Paulaurora on Feb 16, 2014 21:28:48 GMT -6
I will do it tomorrow and let u know what I have
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Post by sempar on Feb 17, 2014 20:56:23 GMT -6
The ground for the EBCM is through the connector C1. Two grounds, F ( BLK/WHT wire) and G (BLK wire) these wires run through the main harness and split off at the engine left front and go to ground G104 at the bottom left front of the engine, just ahead of the vertical auto trans pan. No ground for the BPMV, since its purely mechanical, operated by solenoids that are housed in the EBCM.
John
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tim1993
Aurora Driver
99 Oldsmobile Aurora 4.0L V8
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Post by tim1993 on Feb 17, 2014 22:28:23 GMT -6
my car use to do the same thing but it stopped but i had 2 wheel bearings goin bad on my car and i noticed that when i bought the new ones for the front right side it had the full assembly with the ABS sensor on it and once it was put on i havent had a problem since dont none of my lights come on except the fog light symbol on the dash. The abs dont come no more well it havent been on in quiet a while actually.
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Paulaurora
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Post by Paulaurora on Feb 17, 2014 23:02:00 GMT -6
sorry I couldn't get to the car all snowed in and more snow coming tonight. PM me ur email I will send you some info from the Manual that might help
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Post by LAurora on Feb 18, 2014 22:53:08 GMT -6
Sempar: Thanks for the heads up and clarification. Is it possible to do a continuity test on them with a multimeter? If so, where should I be hooking up?
Paulaurora: I pm'd my email.
Tim: I actually replaced both front hubs within the past two years. I'm thinking it highly unlikely that the sensors went bad, especially since there is no play in the wheel to indicate that the hub itself went bad.
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tim1993
Aurora Driver
99 Oldsmobile Aurora 4.0L V8
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Post by tim1993 on Feb 19, 2014 7:39:53 GMT -6
oh ok well that option is out the window but i hope you find out was causing the light to pop on and off like that i know mines stop but i did have a problem one where my car was skipping and it threw off my abs brake sensors on all 4 wheels it was saying some crazy stuff but the brakes still worked fine and no ABS light wont on idk but its fine now...... good luck man
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tigger
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Post by tigger on Feb 19, 2014 21:57:48 GMT -6
C1242 Pump Motor Circuit Open C1243 Pump Motor Stalled
It's either your EBCM or BPMV, haha, lotta help right? Unless you like your local GM stealer, I'd go get the assembly at a Pull a Part or whatever you have locally. Look for JL9 w/JL4 RPO's. $400+ each new.
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tim1993
Aurora Driver
99 Oldsmobile Aurora 4.0L V8
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Post by tim1993 on Feb 20, 2014 4:42:39 GMT -6
damn thats a lot lol but i mean the ABS light havent been on in a while and the car runs fine but i was told when the car starts to skip it makes some of the sensors go crazy when there is really nothing wrong with anything.
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Paulaurora
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Post by Paulaurora on Feb 20, 2014 7:20:48 GMT -6
Email sent.
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Paulaurora
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Post by Paulaurora on Feb 25, 2014 9:16:03 GMT -6
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Post by LAurora on Feb 28, 2014 20:37:39 GMT -6
Thanks for the diagram update Paul, I appreciate it. I put my ABS hunt on hold for a while because the normal braking works fine, and it just got too frustrating. I also got some new valve cover gaskets and wanted to replace them to stop an oil leak... which of course caused a new problem you can read about here. aurorah.proboards.com/thread/28149/vacuum-leakbasically it seems like the more you work on these cars, the more problems that seem to magically appear.
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tim1993
Aurora Driver
99 Oldsmobile Aurora 4.0L V8
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Post by tim1993 on Mar 1, 2014 6:41:29 GMT -6
yea i know right its tryna tell you it wont everything replaced but i had vacuum leak in my car too the man wouldnt even let me take the care home when i first put my down payment on it cause he said he was gonna get the problem fixed and on top of that he had to get it inspected.
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Post by synthesis on Mar 14, 2014 16:00:10 GMT -6
Don't go spending money on a EBCM yet... Fix your steering sensor and then see if you still get codes for the EBCM.
I repaired mine. It was a cold solder joint inside the EBCM unit.
The EBCM unbolts from the brake solenoid body. You can open the unit with a little bit of effort and re-heat all of the large solder joints.
That repaired module is on my 2002 Aurora parts car, after the car got rear-ended in November. It worked fine when I reinstalled it, and it works now.
It's an easy fix, just time consuming to remove the module and separate the halves.
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Post by beiland on Jul 24, 2014 20:34:05 GMT -6
Perhaps I am going to have to send this information to that repair shop that is working on trying to bleed my rear brakes on a my 2001 Aurora. They believe that the 'traction control' function (lite on continuously) is keeping them from being able to bleed the brake system. Brian
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Randy T.
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Post by Randy T. on Jul 25, 2014 6:06:19 GMT -6
Make sure and check the front abs wiring, they are known to break on Buicks about 18-20 inches from the hub/bearing assembly, ours is about the same, so we may have the same problem.
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Post by boldsmobile on Jul 27, 2014 4:18:57 GMT -6
Had the exact same intermittent issue with mine. Finally associated it with turning the wheel.
The Wheel speed sensor harness was not properly dressed. When the wheel is turned in one direction , I seem to remember left , the outer edge of the rim would rub on the wire. It eventually exposed bare wire. Once bare the light would turn on when the rim touched it.
You won't find that in a book.
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Post by beiland on Aug 31, 2015 22:06:34 GMT -6
.... The pump motor your codes refer to is part of the anti-lock brake and traction control unit located at the bottom LF corner of the engine cradle. You can't miss it; all the brake plumbing on the vehicle passes through this module. And that pump motor has a chassis ground wire that exits the motor case and is bolted to an adjacent chassis hole. That chassis connection can rust/oxidize. Remove the bolt and apply a dose of wire brush and use star washers on both sides of the terminal when reassembling. A broken chassis ground wire would also be a possibilty. So a bad ground wire on the ABS control module could be a possibility,...or give a bad code for that module?
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