MIL ON, Converter Odor, Poor Performance, and DTC 45 Set

Group Ref.: 6E - Engine Fuel & Emission

Bulletin No.: 476516

Date: August, 1994

SUBJECT:
DTC 45, CONVERTER ODOR, DIMINISHED PERFORMANCE (CHECK CMFI UNIT)

MODELS:
1992-94 CHEVROLET AND GMC TRUCK S/T MODELS AND M/L VAN
1992-94 OLDSMOBILE BRAVADA WITH 4.3L ENGINE (VIN W - RPO L35)

CONDITION:

Some vehicle owners may report one or more of the following:

1. The malfunction indicator (service engine soon) light has illuminated (check for stored DTC 45 - Rich Exhaust).

NOTE:
A previously set DTC 45 may be erased by the time a customer brings the vehicle in for service. A DTC 45 will be cleared from memory:

a. After 50 ignition cycles, if the condition has not recurred since first setting the code.

b. If the ignition switch is turned "OFF" and fuse number 9 (ECM B) is removed for 10 seconds.

2. The vehicle has an H(2)S odor (converter odor, rotten egg smell), especially at idle after the vehicle is fully warmed up.

3. The vehicle has driveability problems (one or more) such as:

- Rough Idle

- Hard Starting when Hot

- Poor Gas Mileage/Fuel Economy

- Diminished Performance

CAUSE:

System/component variability.

CORRECTION:
Perform the following diagnostics to determine if the Central Multiport Fuel Injection Unit may be causing the condition.

1. Connect a Tech-1 or Cams machine to the vehicle.

2. Remove the evaporative emission canister purge hose from the throttle valve unit.

3. Run the engine until the coolant temperature is at least 85~C.

4. Idle the engine for 5 minutes (engine should be in closed loop).

5. Verify the LEGR valve is indicating 5 percent or less actual pintle position. If the LEGR valve is not at 5 percent or less, perform LEGR valve diagnostics first.

6. While engine is idling, read the long term fuel trim (BLM). If the reading is 108 counts (or less), replace the CMFI unit with part number 17113151.

7. After installing the new CMFI unit, run the engine at idle for 5 minutes (same conditions as step 4). Verify that the long term fuel trim has increased above 108 counts.

8. If the counts have not increased above 108, continue diagnosis using the service manual procedures for DTC 45.

9. Reinstall the purge hose to the throttle body.

PART INFORMATION:

Part
Description Number

Central Multiport Fuel Injection Unit 117113151

Parts are currently available from GMSPO.

WARRANTY INFORMATION:





For vehicles repaired under warranty, use the table.