Range Rovers Forum banner

P38 ABS fault (accumulator) 3 amigos ABS Brake TC

945 Views 13 Replies 6 Participants Last post by  pwood999
Hi All, i have the dreaded 3 amigo lights on my 2002 4.6

Brakes started to feel squishy so I figured it was the common accumulator so i replaced it and now the brakes are nice an tight again. Unfortunately the lights are still on even after several cycles of turning the car on and off and driving around.

These are the things I know through the process of elimination:
Brake fluid is level.
With the Key in on position:
ABS Pump is working (fuse and relay good)
Pump cycles on and off. Assume pressure switch okay?
With the truck in park, ABS light is on (normal)
Hand brake switch works when I lift the brake lever (activates light)
However, as soon as I hit the brake pedal the hand brake and TC warning lights come on and the “ABS Fault” message pops up.
Brake lights work (some time ago I removed the lift gate trim and 3rd center brake light but I don’t think this would cause any issues) so i know the brake switch is working.
For good measure I detached the brake switch and cruise control switch from the bracket (but still plugged in) and the issue still occurs.

I also started car while the shifter was in neutral and coasted down hill and sure enough the ABS light disappeared (didn’t touch the brake pedal). I assume this means sensors are good...and of course as soon as I touched the brake pedal the warning lights popped up again.

This leads me to believe it has something to do with the hydraulic pressure of the pedal being pressed. Circling back does this relate to the green pressure switch? Could it be the ABS ECU? Is there a method to test these with a multimeter?

Any other obvious things i should check? I might consider going to a yard and swapping out the ECU to see if that's the culprit.

1 - 14 of 14 Posts
You need to get the error code read, so you know what is causing the problem instead of randomly throwing parts at it. The ECU is very rarely the cause. In this case it sounds like lack of pressure. As the accumulator is new, it should be good. Did you do a full bleed as per RAVE? Normally that's not necessary, but because your original symptoms were a spongy pedal, there may very well be air (or nitrogen) in the system.
i did not bleed the system yet. My understanding is that the spongy pedal was due to the bad accumulator. Once I replaced it the pedal feel was like new. Yes, i did plan to have to code read...just needed to find a place that would do it without charging too much. thanks!
+1 on the brakes needing bleeding by the book. Because you have a powered system a spongy brake pedal is caused by air in the hydrostatic circuit, air in the power circuit will give you the 3 amigos and a delay between you pressing the pedal and the brakes coming on.
alright here are the fault codes as shown by a Solus Legend.

157 Pump Pressure - (switch fault)
1 Brake switch failure
74 Pump Pressure - (switch fault)
79 Pressure Switch failure (short to another)
Clear the faults, bleed the brakes as per RAVE, then try it and see if any faults come back. Don't forget that a fault can only show what it thinks is the problem so a switch fault could be because the switch hasn't closed (or opened) within what the ECU considers to be the correct length of time. So it doesn't have to be the switch, it can just as equally be a weak pump or air in the system so it never achieves the correct pressure for the switch to change state.
ah thanks for explaining it like that. My logic was to replace any offending parts 1st so i didn't have to re-bleed if i had to open the hydraulic circuit again.

I know there is a specific process for bleeding the brakes on the P38. This will be a solo job for me...do you know if the Motive power bleeder will work on the P38? I can't seem to get a definitive answer searching the various forums.
AB lists it as compatible with at least 1 positive P38 review.

No it won't, a power bleeder won't work, you have to follow the process. Using a lump of wood instead of your foot can work or you need to rope in an assistant (small children are usually very happy to help, it makes them feel grown up!).
  • Like
Reactions: 1
From the little I remember on the p there is a bleeder on the block under the hood so not sure if you have done that one. After I did our P accumulator I had to crack that bleeder every now and then and usually a bubble or 2 which firmed the pedal nicely. At least it is the easiest thing to do as a start. I never had the lights (thankfully) so best luck with that.
i finally got around to doing a solo brake bleed/flush. sloooow process. Anyway, cleared out some gunky fluid so that's reassuring. I wasn't optimistic that it would clear the faults and i was right. Same deal, start her up and ABS comes on and turns off if i coast with out touching the brake pedal. As soon as I hit the brake pedal the 3 lights come on. What i did notice this time around was the center brake warning light flickered a couple times. I don't recall seeing this before although it's entirely possible i just didn't notice it. Also, a couple months ago i was out on a washboard fire road and the rough terrain must've jarred something loose because for a moment the TC kicked on and the warning lights turned off. Of course that was short lived and the warning returned a minute later.

question, i am assuming the faults are still stored in memory. As noted above, the warning lights don't turn on until i hit the brakes. Am i correct in assuming that the warning lights (ECU) are reacting to a existing/real fault condition and not triggered by the faults in memory? I ask because the local shop charges $50 just to read and clear the ABS faults.

what does the community suggest i try next?

See less See more
Middle brake light doubles as a low fluid warning as well as a parking brake warning, so the flickering might be simply because you are low on fluid. Level must be checked with teh ignition on after the pump has stopped pressurising the system.
the whole process of bleeding the brakes and constantly topping off the fluid reservoir forced me to keep and eye on the level. It's just at the top end of the max line.
I have had alsorts of wierd and wonderful issue with the abs on my 1997, One issue was a dry solder joint on the motor connection, pump would run sometimes but not others. Fixed that but the pump still ran intermitently. A couple of day ago i decided to give the fuse box some attention, took out all relays and fuses, removed the fuse box, took out the PCB, checked and cleaned everything. Put it all back together and for the last three days no issues. The message centre even started to report better fuel economy (from 10mp to 15). The engine even feels more responsive. The voltage shown from the ODB plug is constant in the high 13's even with the AC cranking.
i finally got around to doing a solo brake bleed/flush. sloooow process. Anyway, cleared out some gunky fluid so that's reassuring.

what does the community suggest i try next?

It's not possible to properly bleed the brakes on your own, unless you have extremely long arms so you can reach brake pedal, ignition & bleed valves at same time !!

Any assistant that can follow instructions on when to press the pedal (slowly) and when to switch ignition on will do.

Squishy brakes is almost certainly air in the system.
1 - 14 of 14 Posts