ABS Fault C1381, and the fix.

[shtu]

Just minutes before I started work to replace the clutch, the ABS system failed. Annoying, but actually really good timing, as it meant I could rule-out the work to replace the clutch being the cause.

As I spent a fair amount of time working out what was going on, may as well write it up.



The Fault Code

C1381 - Fault: recirculation pump supply.
From - Local
Status - Permanent
Characterisation of the fault - Short circuit to positive or short circuit to earth or open circuit.



Initial Tests via Diagbox

The ABS module was communicating, and measurements could be taken, and tests run. (Which after the error code was the first clue, it must have multiple power supplies)

The only test that did not produce the expected results was the ABS pump test. While the test didn't fail, the pump did not run. Other tests of the ABS valves worked, and the valves could be heard operating.



Fuse Checks

More out of hope than any real thought it would work, the fuses above the battery, and in the underbonnet fuse box were all removed, cleaned and tested.

As expected, no change, but an easy thing to try.

The earth points in that area had already been cleaned up while I was doing the clutch recently.



Wiring Diagram

Looking at the wiring diagram, there are two "paths" for power to the ABS unit,

- via the BSI module inside the car.
- via the PCF module (the underbonnet fuse box) then through a relay mounted on the front of that.

I decided to start with the simplest, easiest thing to get at, rather than grubbing about in the footwell or under the wheelarch - the relay.



The Relay

Tacked to the front of the fusebox are two relays. One held on with a nut, the other with a plastic rivet. It's the latter that we are interested in.

The part is an Omron 240107, and is often listed as a fuel pump relay rather than an ABS one.

It's actually two seperate relays in a single casing. The relay itself has 15 pins, not all of them are used in this application,



Relay pinouts

1 - Relay 1 Switched Output
2 - Relay 1 Switch +ve
3 - Relay 1 Switch +ve
4 - Relay 2 Switched Output
5 - Relay 2 Switched Output
6 - Relay 2 Switched Output
7 - Relay 2 Switch Earth
8 - Relay 2 Supply +ve
9 - Relay 1 Switched Output
10 - Relay 1 Switch Earth
11 - Relay 1 Supply +ve
12 - Relay 2 Switch +ve
13 - Relay 2 Switched Output
14 - Relay 2 Switch +ve
15 - Relay 2 Supply +ve

Vehicle Wiring

1 - Relay 1 Switched Output to ABS Module
2 - Relay 1 Switch +ve from F6
3 - Not Used
4 - Not Used
5 - Not Used
6 - Relay 2 Switched Output to ABS Module
7 - Relay 2 Switch Earth
8 - Relay 2 +ve from MF6
9 - Not Used
10 - Relay 1 Switch Earth
11 - Relay 1 Supply +ve from MF8
12 - Not Used
13 - Relay 2 Switched Output to ABS Module
14 - Relay 2 switch +ve from F6
15 - Relay 2 +ve from MF6



Test - Relay Actuators

Once I'd worked out the above, first and easiest test is to see if each realy will close when energised.

Relay 1
Pin 2 +ve, Pin 10 earth - CLICK
(Pin 3 +ve, Pin 10 earth - CLICK - not used by vehicle)

Relay 2
Pin 14 +ve, Pin 7 earth - NO CLICK
(Pin 12 +ve, Pin 7 earth - CLICK - not used by vehicle)

The important thing to note here is that while the relay has two 12v triggers, the car wring does not.

Pin 14 not triggering the relay means that relays isn't closing, so power isn't being fed to the ABS module. At this point, that's confirmed the relay is faulty and should be either repaired or replaced. I opted for a used Omron part, rather than the finest Chinesium.

Testing the replacement, across the same pins as the original

Relay 1
Pin 2 +ve, Pin 10 earth - CLICK
(Pin 3 +ve, Pin 10 earth - CLICK - not used by vehicle)

Relay 2
Pin 14 +ve, Pin 7 earth - CLICK
(Pin 12 +ve, Pin 7 earth - CLICK - not used by vehicle)

All good.



Test - Voltages and Earths

While waiting for the new relay to arrive, may as well test the voltages and earths at the plug, to ensure that we don't have any additional problems like blown fuses, low voltages, high resistance.

With the ignition on, tested out the following plug pins,

1 - output not tested
2 - 12 volts
3,4,5 - not present
6 - output not tested
7 - earth, zero ohms
8 - 12 volts
9 - not present
10 - earth, zero ohms
11 - 12 volts
12 - not present
13 - output not tested
14 - 12 volts
15 - 12 volts



Refit and retest

At that stage, may as well fit the relay and see what happens.

BEEP
BRAKING SYSTEM FAULT

BEEP
ABS FAULT

Bugger.

At this point the hooky chinese Diagbox earned it's keep again, clearing the fault codes from the ABS module fixed this.



The Root Cause

Because I had nothing better to do, I cut the old relay open.

Just as the circuit diagram on the case shows, there's 4 diodes in there, none of which tested well, result of that looks like a short circuit has blown one of the tracks on the PCB.

I did order some replacement diodes in case the replacement didn't show up in time, but haven't got round to installing them, repairing the PCB track, and retesting.



Photos

The vehicle plug in the orientation you'll likely see it - note the pin numbers at each corner of the plug.
https://ibb.co/JxybRDv

The interior of the relay.
https://ibb.co/WFmCFsx

The PCB, showing the blown track.
https://ibb.co/tP0qSdb



A Final Note

While the title says "the fix", there are many reasons that you could receive the same error, eg, fuse or wiring faults.

Don't fire the parts cannon - test.

[jj9]

Interesting post to read, this may help others that experience the same problem. 


.

[Multispacer]

Just minutes before I started work to replace the clutch, the ABS system failed. Annoying, but actually really good timing, as it meant I could rule-out the work to replace the clutch being the cause.

As I spent a fair amount of time working out what was going on, may as well write it up.



The Fault Code

C1381 - Fault: recirculation pump supply.
From - Local
Status - Permanent
Characterisation of the fault - Short circuit to positive or short circuit to earth or open circuit.



Initial Tests via Diagbox

The ABS module was communicating, and measurements could be taken, and tests run. (Which after the error code was the first clue, it must have multiple power supplies)

The only test that did not produce the expected results was the ABS pump test. While the test didn't fail, the pump did not run. Other tests of the ABS valves worked, and the valves could be heard operating.



Fuse Checks

More out of hope than any real thought it would work, the fuses above the battery, and in the underbonnet fuse box were all removed, cleaned and tested.

As expected, no change, but an easy thing to try.

The earth points in that area had already been cleaned up while I was doing the clutch recently.



Wiring Diagram

Looking at the wiring diagram, there are two "paths" for power to the ABS unit,

- via the BSI module inside the car.
- via the PCF module (the underbonnet fuse box) then through a relay mounted on the front of that.

I decided to start with the simplest, easiest thing to get at, rather than grubbing about in the footwell or under the wheelarch - the relay.



The Relay

Tacked to the front of the fusebox are two relays. One held on with a nut, the other with a plastic rivet. It's the latter that we are interested in.

The part is an Omron 240107, and is often listed as a fuel pump relay rather than an ABS one.

It's actually two seperate relays in a single casing. The relay itself has 15 pins, not all of them are used in this application,



Relay pinouts

1 - Relay 1 Switched Output
2 - Relay 1 Switch +ve
3 - Relay 1 Switch +ve
4 - Relay 2 Switched Output
5 - Relay 2 Switched Output
6 - Relay 2 Switched Output
7 - Relay 2 Switch Earth
8 - Relay 2 Supply +ve
9 - Relay 1 Switched Output
10 - Relay 1 Switch Earth
11 - Relay 1 Supply +ve
12 - Relay 2 Switch +ve
13 - Relay 2 Switched Output
14 - Relay 2 Switch +ve
15 - Relay 2 Supply +ve

Vehicle Wiring

1 - Relay 1 Switched Output to ABS Module
2 - Relay 1 Switch +ve from F6
3 - Not Used
4 - Not Used
5 - Not Used
6 - Relay 2 Switched Output to ABS Module
7 - Relay 2 Switch Earth
8 - Relay 2 +ve from MF6
9 - Not Used
10 - Relay 1 Switch Earth
11 - Relay 1 Supply +ve from MF8
12 - Not Used
13 - Relay 2 Switched Output to ABS Module
14 - Relay 2 switch +ve from F6
15 - Relay 2 +ve from MF6



Test - Relay Actuators

Once I'd worked out the above, first and easiest test is to see if each realy will close when energised.

Relay 1
Pin 2 +ve, Pin 10 earth - CLICK
(Pin 3 +ve, Pin 10 earth - CLICK - not used by vehicle)

Relay 2
Pin 14 +ve, Pin 7 earth - NO CLICK
(Pin 12 +ve, Pin 7 earth - CLICK - not used by vehicle)

The important thing to note here is that while the relay has two 12v triggers, the car wring does not.

Pin 14 not triggering the relay means that relays isn't closing, so power isn't being fed to the ABS module. At this point, that's confirmed the relay is faulty and should be either repaired or replaced. I opted for a used Omron part, rather than the finest Chinesium.

Testing the replacement, across the same pins as the original

Relay 1
Pin 2 +ve, Pin 10 earth - CLICK
(Pin 3 +ve, Pin 10 earth - CLICK - not used by vehicle)

Relay 2
Pin 14 +ve, Pin 7 earth - CLICK
(Pin 12 +ve, Pin 7 earth - CLICK - not used by vehicle)

All good.



Test - Voltages and Earths

While waiting for the new relay to arrive, may as well test the voltages and earths at the plug, to ensure that we don't have any additional problems like blown fuses, low voltages, high resistance.

With the ignition on, tested out the following plug pins,

1 - output not tested
2 - 12 volts
3,4,5 - not present
6 - output not tested
7 - earth, zero ohms
8 - 12 volts
9 - not present
10 - earth, zero ohms
11 - 12 volts
12 - not present
13 - output not tested
14 - 12 volts
15 - 12 volts



Refit and retest

At that stage, may as well fit the relay and see what happens.

BEEP
BRAKING SYSTEM FAULT

BEEP
ABS FAULT

Bugger.

At this point the hooky chinese Diagbox earned it's keep again, clearing the fault codes from the ABS module fixed this.



The Root Cause

Because I had nothing better to do, I cut the old relay open.

Just as the circuit diagram on the case shows, there's 4 diodes in there, none of which tested well, result of that looks like a short circuit has blown one of the tracks on the PCB.

I did order some replacement diodes in case the replacement didn't show up in time, but haven't got round to installing them, repairing the PCB track, and retesting.



Photos

The vehicle plug in the orientation you'll likely see it - note the pin numbers at each corner of the plug.
https://ibb.co/JxybRDv

The interior of the relay.
https://ibb.co/WFmCFsx

The PCB, showing the blown track.
https://ibb.co/tP0qSdb



A Final Note

While the title says "the fix", there are many reasons that you could receive the same error, eg, fuse or wiring faults.

Don't fire the parts cannon - test.

Thanks for sharing this detailed breakdown of your fault finding, which I'm sure will be of use to others. One question what was the P/No of the relay that you've ordered?

[Gryffindor]

This was the best true short story I've read in a long time - full of drama and unexpected plot twists. And even scope for a franchise!

[shtu]

Thanks for sharing this detailed breakdown of your fault finding, which I'm sure will be of use to others. One question what was the P/No of the relay that you've ordered?

The part is an Omron 240107, and is often listed as a fuel pump relay rather than an ABS one.

Easy to miss in that textwall.

Searching for 240107 should find it, can also be listed as a "double fuel pump relay", "double fuel injection relay" or less commonly "abs relay".

I can see references for 19203N 96271096 454935 962710 but I didn't use those numbers myself.


Still can't see why they didn't use conventional relays. They're not doing anything clever with this one.