Engine Controls - MIL ON/MAF Multiple DTC's Set
No: 19/03/01/NAS
Ref:
Issue: 1
Date: 07/13/01
MIL Event from Mass Air Flow Sensor
AFFECTED VEHICLE RANGE:
Range Rover (LP) From XA410504 - All Bosch EMS
Discovery Series II (LT) All
SITUATION:
MIL ILLUMINATION: FAULT CODES INDICATE MASS AIR FLOW SENSOR PROBLEMS
Unfastened clips, improper sealing or incorrect filter installation can allow unfiltered air and dirt into the intake. This uncontrolled air flow can result
in MIL illumination and Mass Air Flow (MAF) adaption faults and eventually to sensor contamination.
RESOLUTION:
PROPER INSTALLATION OF FILTERS AND SEALS
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Correct maintenance of the air intake system includes the replacement of the air filter in compliance with the maintenance schedule. More frequent
replacement may be required in extreme use conditions, such as deep water wading or desert driving.
Whenever the filter is replaced, careful execution of the replacement installation is required. It is particularly important that the air filter box cover
and locking clips are fitted correctly after the air filter element has been changed. It is also possible for the "O" ring seal between the air filter box
and the MAF sensor housing to be damaged during the filter change.
PARTS INFORMATION:
Range Rover
PHB102260 Air Filter Housing Assy. Qty 1
^ ESR4238 Air Filter Qty 1
^ PHN100220 Seal Ring Qty 1
MHK100800 MAF Sensor Assy. Qty 1
Discovery Series II
ESR4237 Air Filter Housing Qty 1
^ ESR4238 Air Filter Qty 1
^ PHN100200 Seal Ring Qty 1
ERR7171 MAF Sensor Assy. Qty 1
Contaminated MAF components will require replacement.
WARRANTY CLAIMS:
Claim operation times for Air Filter replacement, MAF sensor replacement and Drive Cycle "C" as appropriate.
Normal warranty policy and procedures apply.
Material allowance is included in labor operation.
REPAIR PROCEDURE
MIL INVESTIGATION AND AIR LEAK CORRECTION
1. Investigation of a MIL event may reveal a range of faults possibly related to uncontrolled air intake:
^ Fuelling adaptions codes (P0171, P0172, P0174, P0175)
^ MAF sensor plausibility codes (P0101, P0102, P0103)
^ Throttle angle plausibility codes.
CAUTION:
It is important that the air filter box cover and locking clips are fitted correctly when the air filter element is changed. Care must be taken
to avoid damage to the O-ring seal between the air filter and the MAF Sensor during the filter change.
2. Inspect the air filter housing for correct alignment between the upper and lower portions.
3. Inspect the O-ring to the MAF sensor for damage.
4. If damage found, replace O-ring.
5. If an uncontrolled air leak is determined, correct the air leak as follows:
^ Clean the airbox of any foreign materials.
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^ Refer to the Workshop Manual Section 19.10.10 and carefully install a new filter. (Figure 1)
^ Verify proper fit of the cover to the filter housing.
^ Install and latch the airbox cover. (Figure 2)
6. If the filter housing cannot be correctly aligned to the filter or the top cover, replace the filter housing.
7. Clear all P-codes.
8. Allow vehicle to idle with the A/C off for 30 minutes to allow FRA/TRA adaptions to adjust.
9. Check for P-Codes.
10. Perform Drive Cycle "C" to validate
11. If no P-codes are set during Drive Cycle "C," the fault was in the filter installation. No additional action is required.
NOTE:
ONLY if plausibility P-codes are set during the drive cycle with a properly fitted filter and a sealed airbox is MAF sensor contamination
indicated as the root cause of the codes.
12. If P-codes are set, refer to the Workshop Manual Section 19.22.25 and replace the MAF sensor unit.
13. Install the filter and housing correctly to prevent uncontrolled air ingress.
14. Clear codes and verify repair by followings steps 8-10 above.
