ABS diagnostics and P1317 code

[TestPoint]

I am working with a Grandson on a 1996 Discovery with both an ABS light and a CEL P1317 code. Both have been on since purchase a few months ago but it is now time to get the annual inspection which it is not going to pass. The P1317 clears but comes back after a drive. Checked resistance of the wheel sensors and they are just over 1k ohm.

We have read forum posts extensively and have explored the RAVE and electrical manuals. Other than seating the sensors, checking the sensor resistance and verifying that wiring harness is connected there doesn’t seem to be much in the way of repair suggestions associated with the OBII code. I must comment that both the RAVE and electrical manuals leave a lot to be desired compared to the Ford and Jaguar manuals that I have.

Right rear sensor got seated a little better this morning but the other three seemed firmly in place. The P1317 was reset and the CEL has been off for two 10 mile trips but it appears on the reader that it is ‘pending’ in the ECM. ABS is still on and has never gone off.

Here comes the questions:

Does anyone know the drive cycle criteria for that code?

Forum posts indicate both that the blink codes for the 1995 model year can and cannot be forced in the ’96 OBDII equipped cars. Which is correct? The blink codes appear to tell you more information than just the P1317.

The Codes:
Code 2-6 - Faulty stoplight switch or wiring. Fuse A5 blown or not fitted
Code 2-7 - Continuous supply to ECU with ignition off. Faulty valve relay or wiring Code 2-8 - No voltage to ABS solenoid valves. Faulty valve relay or wiring.
Code 2-12 - Front right, too large an air gap or the sensor has been forced out by exciter ring.
Code 2-13 - Rear left, too large an air gap or the sensor has been forced out by exciter ring.
Code 2-14 - Front left, too large an air gap or the sensor has been forced out by exciter ring.
Code 2-15 - Rear right, too large an air gap or the sensor has been forced out by exciter ring.
Code 3-0 to 3-9 - Open circuit in connection from ECU to solenoid valve in booster, or in ECU
Code 4-0 to 4-9 - Short circuit to earth in connection from ECU to solenoid valve in booster
Code 4-12 - Front right, wiring to sensor broken or sensor resistance too high.
Code 4-13 - Rear left, wiring to sensor broken or sensor resistance too high.
Code 4-14 - Front left, wiring to sensor broken or sensor resistance too high.
Code 4-15 - Rear right, wiring to sensor broken or sensor resistance too high.
Code 5-0 to 5-9 - Short circuit to 12volt in connection from ECU to solenoid valve in booster, possible earth fault.
Code 5-12 - Front right, intermittent fault with sensor or wiring
Code 5-13 - Rear left, intermittent fault with sensor or wiring
Code 5-14 - Front left, intermittent fault with sensor or wiring
Code 5-15 - Rear right, intermittent fault with sensor or wiring
Code 6-0 to 6-9 - Short circuit between two connection from ECU to solenoid valve in booster.
Code 6-12 - Front right, no output from sensor, sensor may have too large an air gap.
Code 6-13 - Rear left, no output from sensor, sensor may have too large an air gap.
Code 6-14 - Front left, no output from sensor, sensor may have too large an air gap.
Code 6-15 - Rear right, no output from sensor, sensor may have too large an air gap.

Is the ABS light on because of the P1317 or for some other unknown reason? Lots of discussion on pulling fuses to extinguish the ABS light. I would prefer to fix what is broke rather than just turning out the light. What list of things cause the ABS light to stay on?

Any other suggestions on these issues.

 

[joey]

This is what I found on another forum with a little searching:

P1317 Rough Road Line Low Fault
P1318 Rough Road Line High Fault

A while back I had the 'Check Engine' light would come on and some duration (possible weeks) would pass it would go away. The OBD II code that was coming on and off was P1317. This cycle would persist for a while until recently it has not gone away and I needed to smog check my car. P1317 is defined as "Rough Road Line Low Fault", which could imply that the ABS/speed sensor(s) in the wheel(s) are busted and no current can run through them. I believe that you do not need to have ABS to have these sensor since they are used to detect if you are going over some rough road and that your engine is not knocking.

There could be other scenarios that can cause P1317, but in this case it was a bad speed sensor (in appose to the PROM problem). Here was the steps I took to troubleshoot to see if the sensor was really bad.

1. Locate the sensor. It is where the only electrical wires connect near the break calipers.
2. Trace the wire from the sensor back up to the electrical connector socket.
3. With the multimeter, select the Resistance measurement (usually denoted with Omega character) and jab the conductors of the connector (which leads to the sensor) with the multimeter probe. If the multimeter probe is too short, unfold two paperclips and hold each touching the probes and use the paperclips as probe extensions.
4. The reading on the multimeter should show about 1K Ohms (+- 10%). If it shows a very high resistance or infinity (i.e. no reading), then the sensor is dead. Make sure you are correctly touching the conductors within the connector, noting that it is far back and deep. If you are getting P1318, this imples that one of the sensor is shorted, so when probing the sensors, you are looking for a sensor that is showing very low resistance ( <<1K Ohms).

My problem was with the sensor in the front left wheel. So here is the fix to remove the sensor.

The fix:

Materials:
1 Medium flat-head screwdriver
1 Large flat-head screwdriver
1 Electric Multimeter with ability to measure resistance
1 Replacement sensor (~$420 from dealer, arrg! I got mine in Hollywood, CA.)

1. (skip this if dead sensor is in the rear wheel) Turn the front wheel towards the opposite side of the busted sensor; i.e. if bad sensor is on the front left wheel, turn the steering wheel all the way to the right. this will make it easier to access the sensor.
2. Jack up the wheel and remove wheel. This will make it easier to access, you can do it without remove the wheel, but it is more difficult.
3. Locate the sensor.
4. Remove clip holding break line from mud shield using a large flat-head screwdriver.
5. Clean out all dirt around the sensor. You want to make sure no dirt falls into the wheel joint.
6. With a flat-head screwdriver, ply out the sensor (sensor has a little lip for the screwdriver to catch). the sensor does not have any screw holding it in. Push over the break line if it is in the way.
7. Once the sensor is out, pull out the whole unit and wiring that is connected to the sensor.

To install the new sensor, do the reverse.

My explanation of why the code initially came in and out was because the sensor started to fail and the internal connection inside the sensor was coming loose. Once it completely failed, then the error code will not go away. My guess is that it would be difficult to determine which of the sensor is bad if it does work and intermittently starts to fail.

 

[TestPoint]

Thanks for the response!

We have measured the resistance of all four sensors and found them within less than a hundred ohms of the 1,000 spec. So, for the moment, I do not believe that the sensors or sensor wiring is the problem.

Where to go next is the issue.

The blink code trouble list is the next area to test. Eliminating the codes associated with the wheel sensors you are left with:

Code 2-6 - Faulty stoplight switch or wiring. Fuse A5 blown or not fitted
Code 2-7 - Continuous supply to ECU with ignition off. Faulty valve relay or wiring
Code 2-8 - No voltage to ABS solenoid valves. Faulty valve relay or wiring.
Code 3-0 to 3-9 - Open circuit in connection from ECU to solenoid valve in booster, or in ECU
Code 4-0 to 4-9 - Short circuit to earth in connection from ECU to solenoid valve in booster
Code 5-0 to 5-9 - Short circuit to 12volt in connection from ECU to solenoid valve in booster, possible earth fault.
Code 6-0 to 6-9 - Short circuit between two connection from ECU to solenoid valve in booster.

Determining exactly how to evaluate the above is what I am struggling with at the moment. Guess I will start with the brake switch.

Sure would be great if someone could confirm that blink codes could be activated on a OBDII car and if so, how to do it.

Here is the schematic for the brake switch. Obviously, it drives the entire ABS system. Guess I have to get upside down under the dash to verify that the switch works as intended.

 

[joey]

I am pretty sure you have to have Testbook (land rover dealer specific computer) to read the ABS fault codes on the OBDII vehicles.

Have you removed the sensors and cleaned them? D1 is easy, pretty sure it is part of the HUB on the D2, so you should be able to do so. Might just be dirty.

If your brake lights work and cruise works the brake switch is good.

 

[TestPoint]

No TestBook.

Just wandering around in the dark.

So, you advice is to remove the sensors for cleaning before proceeding further?

They all seem to be seated properly.

 

[joey]

On the early D1's ABS is sadly simple. ABS Modulator, ABS Controller, Sensors and Rings.

Personally with as much trouble as I have seen them cause even when working, I disable them when they are mine at least. 30 amp fuse and remove the light from the dash.

But if you want to make them work, you almost have to have the computer hooked up to see what the real issue is.