| Code |
Problem
or Description |
Possible
Causes |
| 12 |
No
reference pulses to ECM.
(All)
-
This
code should flash whenever the “test” terminal is grounded
with the ignition on and the engine not running.
-
If
the engine is running and the code appears, this indicates that the
ECM is not receiving any references from the distributor.
|
- Faulty
or loose EST connector at the distributor.
|
| 13 |
Oxygen
sensor circuit
(All) |
-
Sticking
or misadjusted TPS
-
Faulty
wiring and/or connectors from the oxygen sensor.
|
| 14 |
Coolant
sensor circuit
(All)
-
If
the engine is experiencing overheating problems, rectify before
diagnosing further.
|
-
Faulty
or loose wiring and/or connectors from the coolant sensor.
-
Faulty
coolant sensor.
|
| 15 |
Coolant
sensor circuit
(All)
|
-
Faulty
or loose wiring and/or connectors from the coolant sensor.
-
Faulty
coolant sensor.
-
Faulty
or loose wiring and/or connections at the ECM.
|
| 21 |
Throttle
position sensor (TPS) circuit
(All) |
-
Sticking
or misadjusted TPS plunger.
-
Faulty
or loose wiring/and or connectors at TPS and/or at the ECM.
-
Faulty
TPS.
|
| 22 |
Throttle
position sensor (TPS) circuit
(All) |
-
TPS
misadjusted.
-
Faulty
or loose wiring and/or connections at the ECM.
-
Faulty
TPS.
|
| 23 |
Mixture
control (M/C) solenoid circuit
(1982 to 1984 vehicles) |
-
Faulty
or loose wiring and/or connections at the M/C solenoid and/or at the
ECM.
-
Faulty
M/C solenoid.
|
| 23 |
Manifold
Air Temperature (MAT) sensor
(1985 and later vehicles) |
-
Faulty
MAT sensor.
-
Faulty
or loose wiring and/or connections to the MAT sensor.
|
| 24 |
Vehicle
speed sensor (VSS) circuit
(All)
-
A code 24 should only be set while the
vehicle is in motion. Disregard
code 24 if set when drive wheels are not turning.
|
-
Faulty
or loose wiring and/or connections at the ECM.
-
TPS
misadjusted.
-
Faulty
VSS.
|
| 25 |
Manifold
Air Temperature (MAT) sensor
(1985 and later vehicles) |
- Incorrect
voltage level of signal from the MAT sensor to the ECM.
Should be above 4 volts
|
| 32 |
Baro
sensor circuit
(1982 to 1984 vehicles) |
-
Short
between sensor terminals B and C or faulty wiring therein.
-
Faulty
or loose wiring and/or connections at the ECM (Terminals 1, 21 and
22).
-
Faulty
Baro sensor
|
| 32 |
EGR
system
(1985 and later vehicles) |
-
Faulty
EGR valve.
-
Faulty
or loose wiring and/or connections at the EGR solenoid.
-
Faulty,
loose and/or leaking vacuum hoses to EGR valve.
|
| 32 |
Digital
EGR circuit
(1985 and later 3.1L V6) |
-
Faulty
EGR valve.
-
Open
or short to ground in EGR valve circuit.
-
Faulty
or loose wiring and/or connections of EGR circuit.
|
| 33 |
Manifold
Absolute Pressure (MAP) sensor
(All 1988 and later TBI V8, 1990 and
later TPI V8)
|
-
Faulty
or disconnected vacuum hoses.
-
Faulty
or loose wiring and/or connections at the ECM.
-
Faulty
MAP sensor.
|
| 33 |
Manifold
Absolute Pressure (MAP) sensor circuit
(1985 and later 3.1L V6)
-
High
signal voltage, low vacuum.
-
Engine misfire and low unstable idle can set
code 33.
|
- Faulty
or loose wiring and/or connections in the sensor circuit.
|
| 33 |
Mass
Air Flow (MAF) sensor
(1985
to 1989 vehicles, MPFI V6 and TPI V8)
- Excessive
airflow indicated.
|
-
Incorrect
voltage level at
terminal C on the MAF sensor. Should
be 0.5 volts at idle, 4.7 volts at wide open throttle (WOT)
-
Faulty
or loose wiring and/or connections at the MAF sensor.
-
Faulty
MAF sensor.
|
| 34 |
Vacuum
sensor circuit
(1982 to 1984 vehicles)
|
-
Faulty
or loose wiring and/or connections at the ECM (Terminals 20, 21 and
22).
Faulty
vacuum sensor wiring and/or connections.
- Faulty
vacuum sensor.
|
| 34 |
Manifold
Absolute Pressure (MAP) sensor
(1988 and later TBI V8, 1990 and
later TPI V8)
High
vacuum sensed |
-
Faulty
or loose wiring and/or connections at the ECM.
- Faulty
MAP sensor
|
| 34 |
Manifold
Absolute Pressure (MAP) sensor circuit
(1985 and later 3.1L V6)
Low
signal voltage, high vacuum |
- Faulty
or loose wiring and/or connections in the sensor circuit.
An intermittent open will set code 34
|
| 34 |
Mass
Air Flow (MAF) sensor
(1985 to 1989 vehicles, MPFI V6 and TPI V8)
Low
airflow indicated. |
-
Incorrect
voltage level at terminal C on the MAF sensor.
Should be 0.5 volts at idle, 4.7 volts at wide open throttle (WOT).
-
Faulty
or loose wiring and/or connections at the MAF sensor.
- Faulty
MAF sensor.
|
| 35 |
Idle
Air Control (IAC) circuit
(1987 to 1989 vehicles, MPFI V6 and
TPI V8) |
-
Closed
throttle engine speed is 125 RPM above or below desired (commanded)
idle speed for 45 seconds.
- See
a dealer service department for trouble diagnosis.
|
| 41 |
No
distributor signals
(1982 to 1984 vehicles)
|
-
Faulty
or loose wiring and/or connections at the distributor.
-
Faulty
or loose wiring and/or connections at the pickup coil.
- Faulty
vacuum sensor circuit (see code 34).
|
| 41 |
Cylinder
select error
(1985 and later vehicles) |
-
Terminal
D3 of ECM not properly grounded to engine.
- Faulty
or loose wiring and/or connections to the ECM.
|
| 42 |
Bypass
or EST problem
(All)
|
-
If
vehicle will not start, check wire leading to ECM terminal 12.
- An
improper HEI module can cause this code.
|
| 43 |
Electronic
Spark Control (ESC) system
(All) |
-
Faulty
or loose wiring and/or connections to ECM terminal L.
-
Faulty
or loose wiring and/or connections from the ESC controller to the ECM.
-
Faulty
or loose wiring and/or connections from the knock sensor to ESC
controller.
-
Voltage
at ECM A-B connector terminal B7 should be over 6 volts unless the
system is sensing detonation.
- Faulty
ESC sensor and/or module.
|
| 44 |
Lean
exhaust
(All) |
On
carburetor-equipped vehicles:
-
Faulty
or sticking mixture control (M/C) solenoid.
-
Faulty or
loose wiring and/or connections at the ECM, terminals 9 and 14.
-
Vacuum
leakage at carburetor base gasket.
-
Faulty
or loose vacuum hoses.
-
Faulty
or leaking intake manifold gasket.
-
Air
leakage at air management system-to-exhaust ports and at decel valve.
-
Faulty
oxygen sensor.
On
fuel injection vehicles:
-
Faulty
or loose wiring and/or connections at the ECM.
-
Incorrect
fuel pressure.
-
Faulty
or leaking throttle body gasket.
-
Faulty
or leaking intake manifold gasket.
-
Faulty
or loose vacuum hoses.
-
Water
in fuel.
- Faulty
oxygen sensor.
|
| 45 |
Rich
exhaust
(All) |
On
carburetor-equipped vehicles:
-
Faulty
or sticking mixture control (M/C) solenoid and/or wiring.
-
Fuel
in evaporative charcoal canister and its components indicate rich
condition exists.
-
Faulty
oxygen sensor.
On
fuel injection vehicles:
-
Faulty
or loose wiring and/or connections at the ECM.
-
Incorrect
fuel pressure.
-
Leaking
fuel injectors.
-
Intermittent
bursts of fuel from the injectors at idle indicate a faulty TPS.
- Faulty
oxygen sensor.
|
| 46 |
Vehicle
Anti-Theft System (VATS)
(1985 and later 3.1 V6) |
-
Ignition
key and/or starting procedures incorrect.
-
Open
or short to ground in the VATS decoder module circuit.
- Should
be checked by a dealer service department if engine does not turn
over.
|
| 51 |
PROM
problem
(All) |
-
The
PROM is located inside the ECM and is very delicate and easily broken.
An authorized mechanic should do all diagnostic procedures.
-
PROM
not properly installed in the ECM.
-
Faulty
PROM.
- Faulty
ECM.
|
| 52 |
Fuel
CALPAK
(1985 and later vehicles) |
-
CALPAK
PROM not properly installed.
- Faulty
PROM.
|
| 53 |
System
over-voltage
(1985 and later vehicles, except
5.0L carbureted) |
-
Voltage
at ECM terminal B2 is greater than 17.1 volts for two or more seconds.
- Faulty
charging system.
|
| 53 |
EGR
control error
(1985 and later 5.0L carbureted) |
-
Faulty
or loose wiring and/or connections to EGR solenoid.
- Faulty
or loose vacuum hoses to EGR valve.
|
| 54 |
Mixture
control (M/C) solenoid
(1982 to 1984 vehicles) |
-
Faulty
or loose wiring and/or connections from M/C solenoid to ECM.
- Faulty
M/C solenoid
|
| 54 |
Fuel
pump circuit
(1985 and later vehicles)
|
-
Voltage
at terminal B2 is less than 2 volts for 1.5 seconds since last
reference pulse was received.
-
Faulty
fuel pump relay, circuit and connections.
- Faulty
oil pressure switch.
|
| 55 |
Oxygen
sensor circuit
(1982 to 1984 vehicles)
|
-
Faulty,
loose or corroded wiring and/or connectors at the ECM.
-
Four-terminal
EST wiring harness too close to electrical signals such as spark plug
wires, distributor housing, alternator, etc.
-
Faulty
or loose wiring and/or connections of various sensors.
- Faulty
oxygen sensor.
|
| 55 |
ECM
(1985 and later vehicles)
|
-
Faulty
ground connections to ECM.
- Faulty
ECM.
|
| 61 |
Degraded
oxygen sensor
(1985 and later 3.1L V6)
|
|
my 1990 iroc z tpi 305 is not getting fuel. i checked the pressure from the fuel valve and it was good and i believe my injectors are clogged and i dont know how to un clogg them with out taking them out?
how do i adjust a throttle position sensor on a 1992 TPI camaro 5.0
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