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5B.35
Section 5B
EFI Fuel System
5B
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 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 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.
b. Sensor contaminated or damaged.
c. Exhaust leak.
d. Poor ground path.
e. Pin circuit wiring or connectors.
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.
3. Engine Wiring Harness Related
a. Difference in voltage between sensed voltage
(pin circuit 2) and actual injector voltage
(circuit 45/45A).
b. Problem in wiring harness.
c. ECU-to-harness connection problem.
4. Systems Related
a. Ignition (spark plug, plug wire, ignition coil).
b. Fuel (fuel type/quality, injector, fuel pressure,
fuel pump).
c. Combustion air (air cleaner dirty/restricted,
intake leak, throttle bores).
d. Base engine problem (rings, valves).
e. Exhaust system leak (muffler, flange, oxygen
sensor mounting boss, etc.).
f. Fuel in the crankcase oil.
g. Altitude.
h. Blocked or restricted fuel return circuit to
tank.