Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET1993ASTRO VAN M V6-262 4.3L VIN ZREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTECHNICAL SERVICE BULLETINSCUSTOMER INTERESTO2 SENSOR - RATTLING NOISE/A/T STARTS IN 3RD GEAR
1993 Chevrolet Astro Van M V6-262 4.3L VIN Z
O2 Sensor - Rattling Noise/A/T Starts In 3rd Gear
1993 Chevrolet Astro Van M V6-262 4.3L VIN ZSECTION O2 Sensor - Rattling Noise/A/T Starts In 3rd Gear
FILE IN SECTION: 6E - Engine Fuel & Emission
BULLETIN NO.: 56-65-01
DATE: July, 1995
SUBJECT:
Rattling Noise on Acceleration/Transmission Starting Out in 3rd Gear (Provide Clearance or Replace Exhaust Crossover)
MODELS:
1993-94 Chevrolet and GMC Truck M/L Vans
1994 Chevrolet and GMC Truck T Models
1994 Oldsmobile Bravada
with 4.3L Engines (VINs W, Z - RPOs L35, LB4)
CONDITION
Customers may comment on one or more of the following conditions: A rattling noise on acceleration, transmission starting out in 3rd gear (possible DTC 66, 67, 81, 82) and/or diagnostic trouble codes 13 or 44.
CAUSE
M/L Vans
Oxygen sensor and/or harness pigtail contacting the heat shield due to improper routing of the harness. Sharp edges of the heat shield cuts through the wire insulation.
T Trucks
The rattle noise may be the oxygen sensor and/or harness pigtail contacting the heat shield due to the mispositioning of the oxygen sensor mounting boss. Starting out in 3rd gear may be due to the pink wire (CKT 39) shorting out against the heat shield causing power to be interrupted to the transmission control circuit putting the transmission into backup mode (3rd Gear Starts). Diagnostic trouble codes 13 or 44 may be set due to the oxygen sensor signal wire shorting to or cut through by the heat shield.
CORRECTION
M/L Vans
Refer to the "1993 M/L Van Electrical Diagrams and Diagnosis" manual or the "1994 Driveability, Emissions and Electrical Diagnosis" manual for circuit 39 schematics. Normal circuit diagnostics should be performed first if the problem is constant. If the problem is intermittent, an inspection of circuit 39 (pink/black) in the area of the exhaust heat shields may lead to the problem. Inspect the oxygen sensor wiring and replace the sensor it the insulation has been damaged. Re-route wiring harness as needed to protect harness. Clear any codes and test drive.
T Trucks
If the oxygen sensor is contacting the heat shield, this condition can be corrected by replacing the exhaust crossover pipe. If the oxygen sensor wire is damaged, the oxygen sensor must also be replaced.
Follow regular Service Manual Procedures in Section 3 of the 1993 or 1994 "S/T Truck Driveability, Emission and Electrical Diagnosis" manual to make above repairs. Clear any diagnostic trouble codes and test drive.
PARTS INFORMATION
P/N Description Qty
10096129 Sensor, Oxygen (1993) 1
25133503 Sensor, Oxygen (1994) 1
15661132 Pipe, Exhaust Crossover (w/ZR2) 1
15672887 Pipe, Exhaust Crossover (w/o ZR2) 1
Parts are currently available from GMSPO.
WARRANTY INFORMATION
For vehicles repaired under warranty, use:
Labor
Operation Description Labor Time
J6372 Sensor, Oxygen Replace Use Published
L2080 Pipe, Crossover Exhaust Replace Labor Operation Time
BULLETIN NO.: 56-65-01
DATE: July, 1995
SUBJECT:
Rattling Noise on Acceleration/Transmission Starting Out in 3rd Gear (Provide Clearance or Replace Exhaust Crossover)
MODELS:
1993-94 Chevrolet and GMC Truck M/L Vans
1994 Chevrolet and GMC Truck T Models
1994 Oldsmobile Bravada
with 4.3L Engines (VINs W, Z - RPOs L35, LB4)
CONDITION
Customers may comment on one or more of the following conditions: A rattling noise on acceleration, transmission starting out in 3rd gear (possible DTC 66, 67, 81, 82) and/or diagnostic trouble codes 13 or 44.
CAUSE
M/L Vans
Oxygen sensor and/or harness pigtail contacting the heat shield due to improper routing of the harness. Sharp edges of the heat shield cuts through the wire insulation.
T Trucks
The rattle noise may be the oxygen sensor and/or harness pigtail contacting the heat shield due to the mispositioning of the oxygen sensor mounting boss. Starting out in 3rd gear may be due to the pink wire (CKT 39) shorting out against the heat shield causing power to be interrupted to the transmission control circuit putting the transmission into backup mode (3rd Gear Starts). Diagnostic trouble codes 13 or 44 may be set due to the oxygen sensor signal wire shorting to or cut through by the heat shield.
CORRECTION
M/L Vans
Refer to the "1993 M/L Van Electrical Diagrams and Diagnosis" manual or the "1994 Driveability, Emissions and Electrical Diagnosis" manual for circuit 39 schematics. Normal circuit diagnostics should be performed first if the problem is constant. If the problem is intermittent, an inspection of circuit 39 (pink/black) in the area of the exhaust heat shields may lead to the problem. Inspect the oxygen sensor wiring and replace the sensor it the insulation has been damaged. Re-route wiring harness as needed to protect harness. Clear any codes and test drive.
T Trucks
If the oxygen sensor is contacting the heat shield, this condition can be corrected by replacing the exhaust crossover pipe. If the oxygen sensor wire is damaged, the oxygen sensor must also be replaced.
Follow regular Service Manual Procedures in Section 3 of the 1993 or 1994 "S/T Truck Driveability, Emission and Electrical Diagnosis" manual to make above repairs. Clear any diagnostic trouble codes and test drive.
PARTS INFORMATION
P/N Description Qty
10096129 Sensor, Oxygen (1993) 1
25133503 Sensor, Oxygen (1994) 1
15661132 Pipe, Exhaust Crossover (w/ZR2) 1
15672887 Pipe, Exhaust Crossover (w/o ZR2) 1
Parts are currently available from GMSPO.
WARRANTY INFORMATION
For vehicles repaired under warranty, use:
Labor
Operation Description Labor Time
J6372 Sensor, Oxygen Replace Use Published
L2080 Pipe, Crossover Exhaust Replace Labor Operation Time
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.