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5B.39
Section 5B
EFI Fuel System
5B
Code: 32
Source: Oxygen Sensor
Explanation: No change in the sensor output signal.
Expected Engine
Response: “Open loop” operation only, may
cause a drop in system performance
and fuel efficiency.
Possible Causes:
1. Engine Wiring Harness Related
a. Pin circuit wiring or connectors.
Pin 10 for “35 Pin” (MA 1.7) Metal-Cased
ECU.
Pin 11 for “24 Pin” (MSE 1.0) Plastic-Cased
ECU.
Pin 20 for “32 Pin” (MSE 1.1) Plastic-Cased
ECU.
2. Oxygen Sensor Related
a. Sensor connector or wiring problem.
b. Sensor contaminated or damaged.
c. Sensor below the minimum operating
temperature (375°C, 709°F).
d. Poor ground path from sensor to engine
(sensor grounds through shell, see Oxygen
Sensor section).
Code: 33
Source: Oxygen Sensor/Fuel System
Explanation: “System too rich.” Temporary fuel
adaptation control is at the upper limit.
Expected Engine
Response: Erratic performance. Will run rich
(smoke).
Possible Causes:
1. Fuel Supply Related (nothing lean – only rich)
a. Restricted return line causing excessive fuel
pressure.
b. Fuel inlet screen plugged (in-tank fuel pump
only).
c. Incorrect fuel pressure at fuel rail.
2. Oxygen Sensor Related
a. Sensor connector or wiring problem.
b. Sensor contaminated or damaged.
c. Exhaust leak.
d. Poor ground path.
e. Pin circuit wiring or connectors.
Pin 10 for “35 Pin” (MA 1.7) Metal-Cased
ECU.
Pin 11 for “24 Pin” (MSE 1.0) Plastic-Cased
ECU.
Pin 20 for “32 Pin” (MSE 1.1) Plastic-Cased
ECU.
3. TPS Sensor Related
a. Throttle plate position incorrectly set or
registered during “Initialization.’’
b. TPS problem or malfunction.
4. Engine Wiring Harness Related
a. Difference in voltage between sensed voltage
(pin circuit 17 for metal-cased ECU, pin
circuit 2 for plastic-cased ECU) and actual
injector voltage (circuit 45/45A).
5. Systems Related
a. Ignition (spark plug, plug wire, ignition coil.
b. Fuel (fuel type/quality, injector, fuel pump, fuel
pressure.
c. Combustion air (air cleaner dirty/restricted,
intake leak, throttle bores).
d. Base engine problem (rings, valves).
e. Exhaust system leak.
f. Fuel in the crankcase oil.
g. Blocked or restricted fuel return circuit to tank.
6. ECU/Harness Related
a. ECU-to-harness connection problem.
Code: 34
Source: Oxygen Sensor/Fuel System
Components
Explanation: Long term fuel adaptation control is at
the upper or lower limit.
Expected Engine
Response: System operates “closed loop.” No
appreciable performance loss as long
as the temporary adaptation can
provide sufficient compensation.
Possible Causes:
1. Oxygen Sensor Related
a. Sensor connector or wiring problem.
b. Sensor contaminated or damaged.
c. Exhaust leak.
d. Poor ground path.
e. Pin circuit wiring or connectors.
Pin 10 for “35 Pin” (MA 1.7) Metal-Cased
ECU.
Pin 11 for “24 Pin” (MSE 1.0) Plastic-Cased
ECU.
Pin 20 for “32 Pin” (MSE 1.1) Plastic-Cased
ECU.
2. TPS Sensor Related
a. Throttle plate position incorrect during
“Initialization” procedure.
b. TPS problem or malfunction.