Thread: They're back..the 3 of them

A wiring problem would be my guess given you've got open circuit on two and communication issue between the Engine and SLABS ECU's.

AMIGOUSB (2).TXT

Hi guys,
I have attached my most recent diagnosis from my amigos reader.
As Offtrack suggests, most likely a wiring issue, but I cannot trace any obvious failures...broken leads or connectors etc. Any advances?

Thanks

I recently saw a how to AFAIR on a UK site where the wires under the shuttle valve assembly wear through the insulation. If you suspect wiring maybe that is it.

Regards Philip A

With the open circuit valve errors, just check for frozen pistons in the respective callipers. Had this error (and the short circuit error) when sorting out mine recently. I also had the SVS electric failure, but did the bypass trick (option B ?) and it was cured.
Cheers,
Steve

Let's look at the facts:

SLABS ECU uses smart power switches manufactured by a company called Infineon Technologies to control solenoids in both the ABS modulator (BTS612N1) and the SLS system (BTS712N1). These smart switches can detect problems with the circuits they are directly connected to. This problem reporting is limited to open circuit, short circuit to supply voltage, over temperature, and under/over voltage in the connected circuit.

This means for a fault to be reported the problem must lie in the circuit that is reporting the fault. The circuit consists of the ECU, power supply, earth, wiring, and the solenoids in the modulator block. There is no way for mechanical failure in the braking system to trigger a fault.

The connections relating to the faults are:

SLABS ECU
C506-1 Front left outlet solenoid valve (SW - grey with white trace)
C506-10 Rear right outlet solenoid valve (SP - grey with purple trace)

ABS Modulator:
C501-1 Front left outlet solenoid valve
C501-10 Rear right outlet solenoid valve

Pins 1 and 10 are both at the same end of the plug at the modulator, with an empty slot between them.

I'm not 100% how spot on this information is but according to WABCO Type D truck docs (same basic system as the D2) the modulator solenoids should measure 4.0-9.0ohms resistance between supply and ground. You can test this by measuring between the supply pins (1 and 10) and ground at the modulator with the plug removed. If that is ok, work your way back by plugging the connector back in and back probing the connectors. Finally measure at the SLABS ECU plug. With each step you are measuring more of the system and that will help isolate the fault. The only thing that it won't help is testing the ecu and ecu plug.

ADD: I've just checked the resistance on the solenoids on my ABS Modulator and they are measuring 3.5ohm. I'd put the variance down to the accuracy of my meter but it is pretty close to what is suggested above. Anything that is substantially off - less than two-three ohms or more than ton ohms is likely to point to problems in the modulator block. The other gotcha is the ECU seems to interfere with resistance readings so you'll need to unplug at the SLABS ECU to measure the harness resistance.

cheers
Paul

hi all been there done that my series 2 td5 manual 2000 model drove me mad short trip they i eventualy left them on drove it for two years through the gulf
up the cape water crossings the lot sold it bought a 98 defender never looked back was in a caravan park one day talking to a bloke with the same model he was some kind of tech pulled the modulator to bits faulty earth he reckons, fixed it no problems for the last 12 months not a disco fan myself
to many dramas good luck