High negative LTFTs on Subaru Tribeca

[LPGC]

Unlikely but... The LPG system could be wired to the vehicle's canbus / OBD, on some vehicles an LPG system connection to canbus can cause canbus problems and lead to problems like those you're seeing or even worse, example on some Mercs connecting the LPG ECU to canbus or even just connecting a code reader to OBD can prevent the engine start button working and/or put the gearbox ECU into limp mode. You could try pulling the LPG system's fuses to see if the problem goes away, if it does it would point to the above problem and the cure would be to disconnect the LPG system from canbus.

[rich r]

I'd certainly agree that a low battery can cause all kinds of errors on canbus equipped Subarus (that's around 2002 onwards, depending on model line). On the Gen IV Legacy/Outback it's very common for the body ECU to take longer to boot up, so it misses all the other units that talk to it starting up and sending their status in. So you find seemingly unrelated things like the radio not working (because it needs to check against the body ECU to check it's in the right car). Charge the battery, clear the codes and they don't come back when that happens.

Maybe at least some of the codes will go away too on yours once the battery issue is sorted.

[rich r]

Hi Rich, Thanks for the recent recommendation, Outback conversion booked in for Jan 22nd.
Cheers, Simon.

I assume that was Mark's very black Japanese import Outback 3.0?

[LPGC]

Hi Rich, Thanks for the recent recommendation, Outback conversion booked in for Jan 22nd.
Cheers, Simon.

I assume that was Mark's very black Japanese import Outback 3.0?

That's the one, seems to need a PAS pump. Told me you took him out for a go in yours.
Converted a few none Subaru's since then, supercharged F type next week.
Thanks again Rich

[DJB1]

New battery fitted - no difference to fault codes. But we now do have a P0500 code (wheel speed sensor). The C codes that I read off the car's own self-diagnostics have been no help whatsoever. From what I've read, the P0500 is only linked to the front wheel speed sensors. I got my son to check the resistance of the fronts and we found that the left was short circuit. On removal, it has been worn down by the hub magnetic ring. This is quite a common failure mode of a front wheel bearing. New hub and ABS sensor ordered.

Regarding the wiring of the LPG, I know that a wire from the LPG loom is soldered to the OBD connector under the dash. Anyway, I am extremely hopeful that the warning light will go out once the above fix has been carried out.

[DJB1]

Replacing the FL wheel speed sensor hasn’t fixed the problem. We still have the P0500 which means the car is in limp home mode and reading the chassis codes, we have C0231, C0251 and C0272. Apparently you can only read 3 codes at a time so there may be more. If I believe these codes (added to previous ones as well) then it suggests that all the wheel speed sensors are defective. This is clearly unlikely and suggests either failure of the ABS/VDC controller or an electrical fault.

Where will I find the fuses for the BRC system? I’ll start by unplugging these, then I’ll follow the service manual flow diagram for wheel speed sensor DTC.

[Brian_H]

There should be a fuse close to the battery terminal on an inline connector, this will disconnect the battery feed, There will also be another feed coming from somewhere as an ignition switched feed, might be fused or might not be. typically this comes off the petrol injector circuit but could be off anywhere else depending on the installer.