DIY ABS diagnostics

[jnoshea]

Does anyone have any instructions to make a diagnostic tool for the ABS on a 1995 300Tdi discovery? Haynes maual just says that if the ABS warning light is on take it to the dealer (yeh right). The workshop manual is a little more helpful in that it tells you where the diagnostic plug is.  Presumably this plug just sends out simple electronic codes (e.g. voltages on certain pins) to indicate what the problem is.  Surely someone has built something to read these codes already, or knows of a similarly DIY solution. :D

[jnoshea]

Oh, and before Andrew says the Haynes manual has instructions to make a test plug...mine doesn't so if you have a copy that does, please copy the instructions for me  [-o<

[Sharpshooter]

Does anyone have any instructions to make a diagnostic tool for the ABS on a 1995 300Tdi discovery? Haynes maual just says that if the ABS warning light is on take it to the dealer (yeh right). The workshop manual is a little more helpful in that it tells you where the diagnostic plug is.  Presumably this plug just sends out simple electronic codes (e.g. voltages on certain pins) to indicate what the problem is.  Surely someone has built something to read these codes already, or knows of a similarly DIY solution. :D

Firstly, why is the light on??

I would find an independant garage with the facilities. Thay are cropping up all over the place now. I doubt youll find instructions on how to make one. If it were that simple, everyone would have one. :D

[jnoshea]

Does anyone have any instructions to make a diagnostic tool for the ABS on a 1995 300Tdi discovery? Haynes maual just says that if the ABS warning light is on take it to the dealer (yeh right). The workshop manual is a little more helpful in that it tells you where the diagnostic plug is.  Presumably this plug just sends out simple electronic codes (e.g. voltages on certain pins) to indicate what the problem is.  Surely someone has built something to read these codes already, or knows of a similarly DIY solution. :D

Firstly, why is the light on??

I would find an independant garage with the facilities. Thay are cropping up all over the place now. I doubt youll find instructions on how to make one. If it were that simple, everyone would have one. :D

Light came on after a trip to Langdale Quest.  The ABS system as a whole is not that complicated.  The self-test performed by the ABS system on startup will have stored a code which identifies the faulty component or connection.  This (probably simple) code should be readable from the diagnostic plug.  Probably just a sensor plug loose or mud lodged somewhere, but it would be nice to know where to start looking.

[Range Rover Blues]

The Haynes for the Range Rover has it in, albeit in the suppliment (thicker than the rest of the manual) but I wouldn't guarantee that it's the same ABS unit, just a good chance.  If you can identify the plug next to the ABS processor then you need to find a plug on a scrapper that fits it.  Chances are it's going to have a loop from the loom to the other side of the plug, so by removing the blank you break one connection, if this helps to identify it.

[Sharpshooter]

Does anyone have any instructions to make a diagnostic tool for the ABS on a 1995 300Tdi discovery? Haynes maual just says that if the ABS warning light is on take it to the dealer (yeh right). The workshop manual is a little more helpful in that it tells you where the diagnostic plug is.  Presumably this plug just sends out simple electronic codes (e.g. voltages on certain pins) to indicate what the problem is.  Surely someone has built something to read these codes already, or knows of a similarly DIY solution. :D

Firstly, why is the light on??

I would find an independant garage with the facilities. Thay are cropping up all over the place now. I doubt youll find instructions on how to make one. If it were that simple, everyone would have one. :D

Now you say that you just reminded me. A freind of mine was saying the other day that his mate bought a brand new range rover. He thought he would take it off road, and half way round the ABS light came on.  Being the type of guy who could afford a Brand New RR, he went to the dealership explaining the light.  The mechanic said "Have you been off road in it sir?" to which he said "Yes"

"Arr that will be the problem then sir, The mud has knocked the ABS sensors out of adjustment"

To which he replied "So ive just bought a £60k LR and cant take it off road??????????"

Light came on after a trip to Langdale Quest.  The ABS system as a whole is not that complicated.  The self-test performed by the ABS system on startup will have stored a code which identifies the faulty component or connection.  This (probably simple) code should be readable from the diagnostic plug.  Probably just a sensor plug loose or mud lodged somewhere, but it would be nice to know where to start looking.

[jnoshea]

I've found the following instructions on the web for identifying and resetting ABS fault codes in Discoveries and Range Rovers.  I haven't tried it yet, I'll give it a go one evening soon.  If it works, I'll put it in the workshop section.

_______________________________

Turn off the ignition before you start. You then need to pull the ABS warning Relay. Its a small square plug that has a green base and is the relay closest to the front of the seat. With a pen and paper handy, find the blue 4 pin connector under the front of the driver's seat on the RR (or under the black, cardboard lower dash on the Disco-1) and jumper the black to black/pink wire with the key on – a paperclip will work. The ABS light will first flash a long then short blink to indicate the system is beginning diagnostic mode. Then you will start to get your flash sequence. Don’t panic because the code sequence will repeat. Every code starts with 2 pulses on (2.5s each) and then a series of pulses which are the rest of the code. Every code contains two “groups” or “sets” of flashes (i.e. blink, blink, pause, blink, blink, blink, blink, blink, blink would be code 2-6 or “Stop Light Switch Fault…see codes below.) Once you have the code, you can clear the code by removing the jumper while the sequence is flashing. It is possible, as it was in my case, that you have more than one code in memory, so don’t be discouraged if you clear the first sequence only to see another begin.

Here are the codes:

2-12 Front Right
2-13 Rear Left
2-14 Front left
2-15 Rear Right

Reason: Too large an air gap, or sensor has been forced out by exciter ring – try tapping sensor back into place.

5-12 front right
5-13 rear left
5-14 front left
5-15 Rear Right

Reason: Sensor wire has an intermittent fault – check connection(s).

6-12 front right
6-13 rear left
6-14 front left
6-15 rear right

Reason: no output from sensor. Sensor may have too large an air gap. Try tapping in sensor(s), check connections.

4-12 Front right
4- 13 rear left
4- 14 front left
4- 15 rear right

Reason: Wiring to sensor is broken or sensor resistance is too high. Inspect wiring at sensors.

Code 2-6: Stop light switch - faulty switch or wiring. Replace brake light switch.

Code 2-7: Continuous supply to the ECU with the ignition off. Faulty valve relay or wiring.

Code 2-8: No voltage to ABS Solenoid valves. Faulty valve relay or wiring.

Codes 3-0 to 3-9: Open circuit or connection from ECU to solenoid valve in booster, or in ECU.

Codes 4-0 to 4-9: Short circuit to earth from ECU to solenoid valve in booster.

Codes 5-0 to 5-9: Short circuit to 12 volts in connection from ECU to solenoid valve in booster. Possible earth fault.

Codes 6-0 to 6-9: Short circuit between two connections from ECU to to solenoid valve in booster.
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Sounds worth a try.  I'll let you know how I get on.

[Spooky]

Try checking your wheel bearings for excess play - this can cause the sensors to 'think' that they're too far away (thus registering a fault), and frequently occurs after an off-roading session ...

[jnoshea]

Try checking your wheel bearings for excess play - this can cause the sensors to 'think' that they're too far away (thus registering a fault), and frequently occurs after an off-roading session ...

Thanks for the tip Spooky.