Oxygen Sensor Diagnosis

Bulletin # P89-001

Section: Product

Dated: 01/10/89

Subject:
OXYGEN (LAMBDA) SENSOR DIAGNOSIS

To: ALL RANGE ROVER DEALERS

Oxygen sensors produce a small voltage which ranges from slightly above 0.0 to nearly 1.0 volt in response to engine exhaust gas mixture. The richer the mixture, the higher the voltage. Failure of the sensors, sensor heaters or wiring problems can trigger the EFI warning light - as can an ignition coil which arcs due to high resistance or poor secondary insulation.

A fault will be registered on the Hand Held Tester (HHT) whenever one of the above conditions occurs. The HHT simply identifies that a fault has occurred. Additional testing may be required if the problem is not obvious, such as an unplugged sensor. The EFI system will only register a fault after 16,000 engine cycles which, at idle, represents about twenty minutes running time. This prevents light activation during "open loop" operation when the vehicle is warming up.

In order to further test the system, you will need a high impedance multimeter with a low voltage D.C. scale. A meter which reads to three digits is preferred.

The diagnosis procedure which is attached to this Service Bulletin should be used whenever the problem is not clear. Proceed step by step until the vehicle is repaired. Once the problem is definitely located, it is not necessary to continue on with the procedure.

Warranty Information:

Service Type: WW
Repair Code: 2T6X
Labor Operation: Step 1: 99.99.08 - .45 hrs.
Steps 1-2: 99.99.09 - .90 hrs.
Steps 1-6: 99.99.10 - 1.10 hrs.
Steps 1-7: 99.99.11 - 1.20 hrs.











OXYGEN SENSOR DIAGNOSIS PROCEDURE