abs and brake light - abs control module ?
Captain
Joined: Jan 2011
Posts: 725
Likes: 2
From: Central Missouri
There are two sensors. Did you change both, or just one, and which one?
Registered User
Joined: May 2013
Posts: 5
Likes: 1
I keep seeing where you guys find the "magic bullet" ie. sensor in the differential or sensor in the transmission. I have done all that and more and still have the problem. Here is what I have done so far.
1. Replaced sensor in differential, clear, no metal shavings on it
2. Replaced sensor in transmission.
3. Completely cleaned battery terminals and all grounds.
4. followed wiring from rear sensor and transmission to engine, no opens
5. Checked level of brake fluid.
6. Replaced ABS controller (truck has rear ABS only).
7. Resistance on rear diff sensor 1.85 ohms.
8. Resistance on transmission sensor approximately 5 ohms.
Note: NAPA even had me try a second transmission sensor just in case.
I have run out of options. the ABS, brake, and check engine light is still on. I still get a P0500 code for speed sensor. The only thing left that I can think of is a broken wire somewhere.
I have worked in electronics and see that the engineers who drew up the wiring diagrams are mentally challenged at best.
1. Replaced sensor in differential, clear, no metal shavings on it
2. Replaced sensor in transmission.
3. Completely cleaned battery terminals and all grounds.
4. followed wiring from rear sensor and transmission to engine, no opens
5. Checked level of brake fluid.
6. Replaced ABS controller (truck has rear ABS only).
7. Resistance on rear diff sensor 1.85 ohms.
8. Resistance on transmission sensor approximately 5 ohms.
Note: NAPA even had me try a second transmission sensor just in case.
I have run out of options. the ABS, brake, and check engine light is still on. I still get a P0500 code for speed sensor. The only thing left that I can think of is a broken wire somewhere.
I have worked in electronics and see that the engineers who drew up the wiring diagrams are mentally challenged at best.
Registered User
Joined: Aug 2013
Posts: 3
Likes: 1
From: Texas
I finally figured out my ABS/Brake light. I followed the service manual troubleshooting and this is what determined the problem:
RWAL DIAGNOSTIC PROCEDURES—TEST 6
RWAL DIAGNOSTIC PROCEDURES—TEST 6
This procedure starts with both the brake warning
lamp illuminated and ABS warning lamp illuminated and RWAL diagnostics cannot be performed.
If you are able to retrieve a DTC from the CAB's memory, then perform RWAL DIAGNOSTIC PROCEDURES
TEST 1.
TEST 1.
1
Turn the ignition key to the OFF position.
Disconnect the 14-way RWAL CAB connector.
Turn the ignition key to the RUN position.
Turn the ignition key to the RUN position.
- Is the brake warning lamp illuminated?
YES
Perform step
Perform step
2
NO
Perform step 8.
Perform step 8.
Step 2
Inspect the level of brake fluid in the master cylinder reservoir.
Is the fluid level correct?
YES
Perform step
Perform step
3.
NO
Find and repair cause of leakage then perform the Verification Test.
Find and repair cause of leakage then perform the Verification Test.
Step 3
• Is the vehicle equipped with a diesel engine?
YES
Perform step 5.
Perform step 5.
NO
Perform step 4.
Perform step 4.
Step 4
Disconnect the harness connector from the differential pressure switch
Hope this helps.
Is the brake warning lamp still illuminated?
YES
Repair the short to ground for the brake warning lamp circuit and perform the
Verification Test.
Repair the short to ground for the brake warning lamp circuit and perform the
Verification Test.
NO
The pressure differential switch has shuttled. Check the
brake system for air in the hydraulic circuit or possible mechanical
damage. Repair as necessary and then perform the Verification Test.
The pressure differential switch has shuttled. Check the
brake system for air in the hydraulic circuit or possible mechanical
damage. Repair as necessary and then perform the Verification Test.
I'll stop pasting there because that is where I found the trouble.
I took the little switch out from the pressure differential block (connected to the master cylinder) and moved the shuttle 'thing' that was grounding the switch and making the light come on. I moved the The shuttle 'thing' with a dental pick. I think there is an easier way but it worked for me.
I'm happy that those darn lights are finally off.
I took the little switch out from the pressure differential block (connected to the master cylinder) and moved the shuttle 'thing' that was grounding the switch and making the light come on. I moved the The shuttle 'thing' with a dental pick. I think there is an easier way but it worked for me.
I'm happy that those darn lights are finally off.
Hope this helps.
Rookie
Joined: Jul 2012
Posts: 75
Likes: 0
From: Greenville, IL.
What is step 8? I've had this problem on the wife's truck for the better part of a year. Replaced sensors, goes off for a day, back on. Flushed fluid. It finally decided to stay on. The brakes work though, not sure about the ABS part. So, step 8? Or is this procedure posted online somewhere? Maybe I won't need step 8.
Veteran
Joined: Sep 2012
Posts: 464
Likes: 4
You mentioned the axle seals had been replaced. When I did my balljoints / u joints I had to remove both front wheel ABS sensors. When I finished the job I had the ABS/brake lights light up. Turns out I accidentally tweaked one of the front sensor brackets putting them back on the spindle so the magnet face was no longer parallel with the phonic wheel. All I had to do was bend one side further inward and the lights went out. Didn't think something so minor would set it off, but it did. Give this a quick check to make sure it's not something as daft as this.