2nd Gen Non-Engine/Transmission DTCs

[AggieJustin]

Will a scan tool pick up DTCs that won't display in the odometer window? Or do all DTCs display in the odometer window if they've been set.



Yesterday morning at startup, my Brake and ABS lights stayed on. The "three trips to ON" trick doesn't display any set codes, just the 'P done'. If the scan tool will pick up other DTCs, I'll run by the parts store tonight and have it plugged in. If not, it's troubleshooting time. Any ideas where to begin?



ABS appears to be functioning normally, and braking performance is the same as usual.



JM

 

[nps]

You may find some codes that a scan tool displays that you won't see in the odo window. I've never seen it, but others have reported that they have had codes that didn't show in the window.



Autozone will scan it for free (if you have any around there).



When you say 'ABS is normal' how did you test it? Sounds like an abs sensor may not be sending to the abs comp.

 

[AggieJustin]

Thanks nps.



The ABS test was pretty basic. Just found a deserted street and laid down on the brakes. Just a quick lockup, then a release like it's always been.



I'll swing by Autozone and see what they come up with.

 

[AggieJustin]

OK, so the ABS test failed the second time around. It's been around 10 start cycles since the first appearance of the lights, so I figured something had to be wrong. I hit my "test track" at lunch and sure enough... no rear wheel ABS. Time to check the service manual for the parts... .

 

[Piston Slapper]

My ABS light came on but at the same time the speedometer quit. I had no rear wheel ABs by your same test. Replaced Wheel speed sensor($30ish)on top of the rear differential to fix it. Don't know if this applies or not if just ABS is out.

 

[DavidC]

Use an ohmmeter. Unplug the speed sensor and ohm across the two pins. Should be approx. 1800 ohms. If four wheel drive w/ABS you also have front sensors. I believe one on each wheel. Same 1800 applies to those.



Dave

 

[AggieJustin]

Thanks David.



I guess it's time to buy another multimeter. The last one didn't survive a trip riding on the bumper of a friend's truck.

 

[DavidC]

Your welcome. Keep us informed.



Dave

 

[AggieJustin]

Here's the update (and a question)...



I pulled the plug off the sensor on the rear axle and tested the resistance across the plug. It came up as 1960ohms. Also verified tonight that it is the rear axle locking up. Is there a range of acceptable values around the 1800ohm number, or is this value enough to say the sensor is bad?



Also, I've got 4 wheel ABS, so I went ahead and tested my front sensors as well. Here's where my question is... Is the only way to get at the sensor to pull the front wheel? Or where is the sensor located? I figured they took their reading off the disc for the brake, but I can't find a way to get to the sensor from the back side. But anyway, I have the wiring diagram for where the sensors connect to the Antilock Brake Controller. So I tested the sensor from the plug. Checking the rear sensor from the plug, confirmed the reading of 1960ohms. The left wheel sensor had a reading of 1144ohms and the right wheel sensor was completely open.



If I have to pull the front wheels to get to the sensors, I'll pull them this weekend to confirm the readings. But it's odd that both of the front sensors are so far off the mark.



JM

 

[DavidC]

Sounds like the right one is a definate. The left is reading pretty low,not quite sure if it is on its way out or not. Yes on the Wheel removal. The back one is probably ok with the higher reading. Be sure to check the wiring on the front sensors at the wheel as ther have been some issues. The 1800 will depend on the meter, test leads etc. I would probably buy both fronts and change them. Good luck.



Dave

 

[AggieJustin]

Thanks David.



Does the lack of signal from the front sensors just shut down the entire ABS system? If so, that explains the fact that the rears lock up since there is no weight back there.



This would also explain why I still have a speedo reading since the rear still appears to be OK



JM.

 

[DavidC]

I believe and what I can decipher from the manual a defective sensor will shut the abs down. It has no source to measure wheel speed effectively. When working properly the two front wheels work independantly of each other and the rear wheels work in tandem.



Dave

 

[AggieJustin]

OK, problem solved.



New ABS sensor on the right front wheel and I'm back in business. Apparently, front wheel ABS sensors are on national backorder right now (not sure what that's all about). But I got lucky and found one in stock at a dealer over the weekend. Actually, got really lucky because I got a good deal on it. I checked with a dealer here in Plano and the price was $73 for the sensor and it would have taken around 5 days to get here. While I was down in Giddings over the weekend, I checked with the dealer there and got the same sensor for $41. Quite a price difference for the same part.