Mil Event From Mass Air Flow Sensor (19/03/01/NAS)

MIL EVENT FROM MASS AIR FLOW SENSOR

TECHNICAL SERVICE BULLETIN

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

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

Vehicle	Part Number	Description	Qty
Range Rover	PHB102260	Air Filter Housing Assy.	1
Range Rover	ESR4238	Air Filter	1
Range Rover	PHN100220	Seal Ring	1
Range Rover	MHK100800	MAF Sensor Assy.	1
Discovery Series II	ESR4237	Air Filter Housing	1
Discovery Series II	ESR4238	Air Filter	1
Discovery Series II	PHN100200	Seal Ring	1
Discovery Series II	ERR7171	MAF Sensor Assy.	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.
   • Refer to the Workshop Manual Section 19.10.10 and carefully install a new filter. (Fig 1 )
     Fig 1: Installing New Filter

     
   • Verify proper fit of the cover to the filter housing.
   • Install and latch the airbox cover. (Fig 2 )
     Fig 2: Installing & Latching Airbox Cover

     
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.