Thread: Decoding and fixing an issue with my D2 V8

According to the LR diagnostic flows:

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P134 = Lambda sensor upstream catalyst bank 1 Drive cycle C:Signal missing.

Oxygen sensor upstream of catalyst bank A (front left hand sensor)

The possible causes of this are:

1. Oxygen sensor heater not functioning correctly.
2. Open circuit C635/15 (O) to C644/2 (O).
3. Open circuit C635/9 (RB) to C644/1 (RB).
4. Connector(s) C644,ECM C635 (B).
5. Oxygen sensor damaged or surface contaminated.

1. Oxygen sensor heater not functioning correctly.

CHECK THE FOLLOWING:
Oxygen sensor heater fault flags are set.

INFORMATION
If the oxygen sensor is not at the correct operating temperature the sensor may appear faulty to the Motronic diagnostics system. This fault should be diagnosed by exploring the oxygen sensor heater faults which will be set if this fault is present.

2. Open circuit C635/15 (O) to C644/2 (O).
OPEN_CIRCUIT
Check resistance > 1MOhm

3. Open circuit C635/9 (RB) to C644/1 (RB).
OPEN_CIRCUIT
Check resistance > 1MOhm

4. Connector(s) C644,ECM C635 (B).
CONNECTOR
Check for connector not correctly latched, backed out pins, damaged pins, corroded pins

5. Oxygen sensor damaged or surface contaminated.
CHECK THE FOLLOWING:
Remove the oxygen sensor and examine the side internal to the exhaust system and the side outside the exhaust system. Both sides of the sensor should be free from contamination. Gas must be able to be absorbed by both sides of the sensor.
Also check the sensor for any mechanical damage or cracks.
INFORMATION
If the oxygen sensor shows signs of damage or contamination that cannot be cleaned it should be renewed.

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If do you need to change the sensor it is part number Part number for the front sensor is MHK100920. A quick sampling of local sellers suggests it will cost you $200-250 for the sensor.

cheers
Paul

Originally Posted by OffTrack

According to the LR diagnostic flows.....

Thanks heaps Paul.

Looks like I've got more reading, researching, and learning to do.

This may be related information, but it seems that the misfire is only present at running temperature.

What is meant by 'check resistance'??

You need to grab a multimeter and check the resistance of the wires between the numbered connectors. You are looking for short or open circuits. If the wire is good resistance will be very low. 0.1 ohms or similar. Open circuit will show up as very high resistance or OL on the meter.

The electrical library PDF on the rave cd shows connector views and pin outs so you can identify the location of connector referred to.

The drive cycle letter refers to a specific state of operation of the engine. There is information either in the workshop manual or the PDF covering the EOBD systems both of which should be on the RAVE cd.

Thanks once again Paul.

About the only thing I've understood so far is "RAVE CD" . I've got one of them (I think). I've actually got a PDF workshop manual, I think that's the same. Being a 'layman', I think I need someone to translate your posts for me.

You're obviously very knowledgeable on these types of things. Thanks once again for your input and explanations.

I'll sit down tonight with a couple of cans of cola (mixed with bourbon of course ), and see if I can learn/understand more from your posts, and then on Sunday, get to work on putting your expertise into practice.

The workshop manual pdf doesn't contain any of the additional material relating to the electrics that is included on the CD.

The electrical library.pdf contains descriptions of how the electrics work and photo most connectors.

C635.pdf

C644.pdf

What the diagnotic flow is doing is guiding you through the steps required to eliminate other possible causes for that fault code before you reach for a new part.

Step 1 is telling to look for fault codes that relate to the O2 sensor heater - if they exist you need fix those codes first.

Step 2 & 3 is basically saying check the wiring from the ecu to the O2 sensor to make sure there isn't a fault there. The easiest way is to hook up a multimeter and check continuity or resistance on each wire. The C644-2 (O) tells you to check from the orange wire at pin 2 of connector C644 to the corresponding wire at the ECU connector.

Step 4 check the plug at the O2 sensor wiring to make sure it is clean and the contacts are undamaged.

Step 5 remove the O2 sensor and check for damage/contamination.

This following is from the EOBD Workbook which is on the RAVE CD. The "Drive Cycle" in the P code result appears to be referring to the test drive cycle which must be carried out when checking to ensure the fault is fixed.

Service Drive Cycles
To ensure that a fault causing a diagnostic trouble code (DTC) has been successfully resolved, drive cycles have to be carried out. Testbook indicates the relevant drive cycles to be carried out following the incidence of a specific P-code.
A driving cycle consists of engine start-up, vehicle operation (exceeding starting speed), overrunning and engine stopping. On OBDII, a drive cycle is simply defined as starting the engine and driving the vehicle long enough to raise the coolant temperature by at least 40° F (if the start- up temperature is less than 160° F).
A complete driving cycle should perform diagnostics on all systems.

The following are the TestBook drive cycles used on Discovery II with V8 engines and Bosch 5.2.1 engine management system:

⇒ Drive cycle A:
1. Switch on the ignition for 30 seconds.
2. Ensure engine coolant temperature is less than 60°C (140°F).
3. Start the engine and allow to idle for 2 minutes.
4. Connect TestBook and check for fault codes.

⇒ Drive cycle B:
1. Switch ignition on for 30 seconds.
2. Ensure engine coolant temperature is less than 60°C (140°F).
3. Start the engine and allow to idle for 2 minutes.
4. Perform 2 light accelerations (0 to 35 mph (0 to 60 km/h) with light pedal pressure).
5. Perform 2 medium accelerations (0 to 45 mph (0 to 70 km/h) with moderate pedal pressure).
6. Perform 2 hard accelerations (0 to 55 mph (0 to 90 km/h) with heavy pedal pressure).
7. Allow engine to idle for 2 minutes.
8. Connect TestBook and with the engine still running, check for fault codes.
⇒ Drive cycle C:
1. Switch ignition on for 30 seconds.
2. Ensure engine coolant temperature is less than 60°C (140°F).
3. Start the engine and allow to idle for 2 minutes.
4. Perform 2 light accelerations (0 to 35 mph (0 to 60 km/h) with light pedal pressure).
5. Perform 2 medium accelerations (0 to 45 mph (0 to 70 km/h) with moderate pedal pressure).
6. Perform 2 hard accelerations (0 to 55 mph (0 to 90 km/h) with heavy pedal pressure).
7. Cruise at 60 mph (100 km/h) for 8 minutes.
8. Cruise at 50 mph (80 km/h) for 3 minutes.
9. Allow engine to idle for 3 minutes.
10. Connect TestBook and with the engine still running, check for fault codes.

cheers
Paul