OK - I've read the threads I can find... My 2002 4.6 started doing the occasional ABS / traction failure when very cold last winter (-25F or so). It comes and goes. The last few days, the ABS fault is on before I even start the vehicle. Then later the TC light comes on. (and message center displays the faults). The sensors seem to be seated OK, but I'm not sure how far they should be in... Is it OK to tap on them lightly with a rubber mallet to make sure they're seated, then try again? Sometimes I notice the beep after the vehicle raises itself if it has lowered itself somewhat during parking.

Is there a fuse I can check? Which one? Any other symptoms you suggest I look for? I was able to rotate the sensors slightly and they seem to be pushed in down to a ring, with maybe a mm or so from the ring to the area where the sensor's diameter gets bigger. Tried to re-start and the ABS/TC lights still come on. Will go drive it next. Pedal feels fine, felt fine after pushing on it 50 times too.

I'm hoping someone has a few ideas / items for me to check myself. Nothing is full of mud since I'm pretty easy offroad with it, but is there anywhere I can direct a hose to try to wash out anything that would interfere with the sensors?

THANK YOU!

 

Did you check the relays?

Mike

 

Does it go away within a few minutes after start up? or is this a random occurrence when driving? If it only occurs when you initially start the vehicle, it may be a bad accumulator or accumulator pump.

 

mlshelton, I have not checked any relays - sorry not sure which ones to check... Any help there? I didn't see anything in other threads. I did check all ABS fuses, pulled, restarted, etc to see if any would reset the fault.

LRScott - it does not go away, though it has happened earlier going over a bump and then will reset on next startup. Accumulator / pump started and stopped within maybe a second (meaning, I think that it's demanding pressure, providing it, and stopping fine). Pedal feels fine... I did push sensors back in & drove it, no help, but again, not sure if I pushed them in much. They were hard to move. OK to tap on them?

 

There's a yellow TC relay and a black ABS one in the under hood fuse panel. Not sure of their #'s off hand. If your pump is starting and stopping fine, and your pedal feels tight, you more than likely have good pressure in the switch. My old P38 is in the shop right now for a related ABS issue - we're supposed to receive a replacement pump / accumulator today. Your symptoms are not the same - you still have brakes.

 

Thanks mlshelton... An update. I drove it to work today and had no issues. Started again, drove it 240 miles on a trip and had no indicators showing, then turned it off and had traction failure on the message display. Started it again and both lights again. No performance issues (except when both lights are lit, ABS is definitely disabled if I mash the brakes)... So something seems to be borderline or intermittent. Any ideas? Thanks again, Mike S.

 

Do you not hear any clicking, or pumping noise? I am wondering how your ABS pump could be working, and would assume it's not if you can tell it). Maybe it's in the pressure switch itself on the pump - if the switch or accumulator don't achieve enough pressure (I think somewhere around the 160 lb range) the pump won't shut off. You'll end up burning out the pump itself. I've been down this road with our P38's before - I wouldn't drive the car myself until resolved, that's a lot of weight to not be able to stop.

 

This morning I put the key to almost start, and the ABS pump came on for 42 seconds and stopped. Then after about 3 minutes, it came on for 1 second and stopped. Pump did not get warm. ABS/TC fault on key to run state (but not started). On the last OK trip, it took about 20 seconds after rolling for the lights to go off (ABS & TC), then no fault, which is fairly common... So maybe the pump is going. On those really cold days last winter, the EAS pump once took about 7 minutes to seal and lift the vehicle (at -25F), never did it again. Sure wish there was an open-source testbook... I seated and unseated the black ABS relay and the 4OA fuse, no help. Could not see a yellow relay labeled TC. There is a silver clip on the pressure switch I couldn't get off, thought I'd test that... Do you have to remove that clip, maybe I can find some tools around here (at my Mother's house)... No voltmeter here either, I guess I'll wait. I wonder if it is a wheel sensor wire since sometimes it will be OK then fault when vehicle lifts itself if low (maybe proximity switch has no power, short, open circuit, etc). Wires looked OK as far as I could see.

Just depressurized the system by pumping the pedal 50 times. ABS pump took 43 seconds to fill it (which means it depressurized overnight, same reading)

 

I might be the accumulator, at least that is what I think...I don't know if 42 seconds is normal, mine takes about that long but, I think the accumulator is going bad on mine and I would rather spend 200 on a new accumulator than a couple grand on the pump. After I replace the fan clutch I will be replacing the accumulator .

 

In addition to the other symptoms, the brake warning light is also now on immediately after 'on' position, until the pump fills the accumulator. It turns off the instant the 'traction failure' message is displayed. I found a local place to take it, just don't have time yet.