I've reverted to this so many times helping others out. The only other place I've seen a troubleshooter this good was browsing the codes at autozone. So HERE! HAVE YOUR OWN! This is not Fiero Specific but still great to have.
CODES CODES CODES
MALF CODES
Code 12 - Reference Pulse
Trouble Code 12 is a special case code that is not logged into the ECM's Non-Volatile Memory (NVM) when detected. When the ignition is "ON" and the ECM detects no ignition reference pulses coming from the ignition module, it illuminates the Service Engine Soon lamp. Code 12 is also used when the ECM is in Diagnostic mode (ALDL Terminal B grounded, key On, engine Off) to signal the beginning or end of a so-called 'diagnostic sequence'. This is when the ECM enunciates each stored code using the instrument panel Service Engine Soon lamp. When in this mode, the ECM will begin by flashing code 12 (on the lamp) 3 times. This indicates the beginning of a diagnostic sequence. It will then flash any codes stored in NVM 3 times each before proceeding to the next code. When all stored codes have been displayed, the ECM will again flash code 12 to indicate the end of the diagnostic sequence. The cycle continues as long as the ECM is in Diagnostic Mode.
Code 13 - Oxygen Sensor Failure
Trouble Code 13 indicates that the exhaust stream oxygen content sensor (O2 sensor) is not responding as expected. When cold, the sensor is 'biased' by the ECM to about 450 millivolts. Before it warms to at least 600 deg F (315 deg C) it acts as an open circuit and when the ECM reads it, it reads the 450 mV bias. The ECM expects the sensor to warm in a short period of time and begin sending its own voltages.
The conditions for setting this code are:
engine running at least 40 seconds and
no code 21 or 22 (TPS errors) present, and
coolant temperature is at least 118 deg F (48 deg C), and
O2 sensor voltage not fluctuating (i.e. steady between 350 and 550mV), and
TPS signal indicates above idle (over 6%), and all the above conditions met for more than 8 seconds
If the conditions for a Code 13 exist, the system will not go "Closed Loop"
Typical causes for this code include:
Defective or degraded O2 sensor
Deposit contaminated O2 sensor (running leaded fuel, RTV silicone deposits etc.)
Corroded/defective O2 sensor connection
Defective sensor ground circuit
Defective connection at ECM
Defective ECM
Code 14 - CTS High
Trouble Code 14 indicates that the Coolant Temperature Sensor (CTS) is reporting abnormally high readings. CTS is used to control fuel mixture, timing, idle speed, TCC and EGR operations among others. The thermistor used has a low resistance when hot, rising as the coolant cools. This error then, indicates a very low resistance in the CTS circuit.
The conditions for setting this code are:
the coolant temperature reported is > 284 deg F (140 deg C),
and the above condition is present for more than 20 seconds
NOTE: A default temperature in the range of 72 to 111 deg F is used while the error is present.
Typical thermistor resistance values are:
DegF DegC Resistance (ohms)
210 100 185
160 70 450
100 38 1,800
70 20 3,400
40 4 7,500
20 -7 13,500
0 -18 25,000
-40 -40 100,000+
Typical causes for this code include:
Severe engine overheating
Defective Coolant Temperature Sensor (resistance too low)
Short circuit in CTS-ECM harness
Defective ECM
Code 15 - CTS Low
Trouble Code 15 indicates that the Coolant Temperature Sensor (CTS) is reporting abnormally low readings.
CTS is used to control fuel mixture, timing, idle speed, TCC and EGR operation, among others. The thermistor used has a high resistance when cold, lowering as the coolant warms. This error then, indicates a very high resistance in the CTS circuit.
The conditions for setting this code are: the coolant temperature reported is < -29 deg F (-34 deg C), and the above condition is present for more than 4 seconds
NOTE: A default temperature of 72-111 deg F is used while the error is present.
Refer to the Code 14 description for typical sensor resistance values.
Typical causes for this code include:
Open circuit in CTS-ECM harness
Defective Coolant Temperature Sensor (resistance too high)
Open sensor ground circuit
Defective ECM
Code 21 - TPS High
Trouble Code 21 indicates that the Throttle Position Sensor (TPS) is reading abnormally high. TPS volts should be close to 0.42 V at closed throttle and rise smoothly in about 0.02 volt increments to a maximum reading of about 4.85 volts at WOT.
The conditions for setting this code are:
The engine is running, and
Code 33 or 34 (MAF error) is not set, and
TPS reading is > 4.90 volts
- or -
TPS reading stays between 2.5 and 4.9 volts, and
MAF reading is < 15 grams/second, and the above two conditions are present for more than 5 seconds
Note: During a Code 21 condition, the ECM uses a default TPS value of 2.6 volts. This will cause the engine to idle very high.
Typical causes for this code include:
Defective TPS
Short circuit in the TPS harness to +5 volt reference
Open sensor ground circuit
Defective ECM
Code 22 - TPS Low
Trouble Code 22 indicates that the Throttle Position Sensor (TPS) is reading abnormally low. TPS volts should be close to 0.42 V at closed throttle and rise smoothly in about 0.02 volt increments to a maximum reading of about 4.85 volts at WOT.
The conditions for setting this code are:
The engine is running, and
TPS reading is < 0.20 volts
Note: During a Code 22 condition, the ECM uses a default TPS value of 2.6 volts. This will cause the engine to idle very high.
Typical causes for this code include:
Misadjusted TPS
Defective TPS
No +5 volt reference to TPS
TPS-return to ECM is shorted to ground or to sensor ground
Defective
ECM NOTE: The TPS must be adjusted to about 0.42 volts at closed throttle for the ECM to auto-zero properly. If necessary, adjust the TPS to bring the voltage up or down to this value at closed throttle.
Code 23 - MAT Low
Trouble Code 23 indicates that the Manifold Air Temperature (MAT) sensor is reporting abnormally low readings. When the air is cold, the thermistor in the sensor has a high resistance, which falls as the air charge warms.
Low readings indicate a possible bad sensor or open in the MAT circuit.
The conditions for setting this code are:
MAT reading is < -40 deg F (-40 deg C)
NOTE: A default MAT value indicating 82 deg F is used while Code 23 is present.
Typical thermistor resistance values are:
deg F deg C Resistance (ohms)
210 100 185
160 70 450
100 38 1,800
70 20 3,400
40 4 7,500
20 -7 13,500
0 -18 25,000
-40 -40 100,000+
Typical causes for this code include:
Defective MAT sensor
Open sensor ground circuit
Dirty or corroded connection(s) at MAT and/or ECM
Open circuit between the ECM and the MAT sensor
Defective ECM
24 - VSS Fail
Trouble Code 24 indicates that the Vehicle Speed Sensor (VSS) is reporting an abnormally low reading when other sensors indicate it should be higher.
The conditions for setting this code are:
No Code 33 or 34 (MAF Error) is present, and
The vehicle speed signal indicates < 4 MPH and
Engine speed is between 1400 and 4400 RPM, and
During a low load condition (LV8 between 50 and 99), and
Transmission not in Park or Neutral, and
All conditions met for more than 20 seconds
If the code was logged when the vehicle was in motion, the following should be checked:
Defective or corroded VSS connections
Misadjusted TPS sensor. The TPS should read about 0.42 volts at closed throttle
Defective speedometer cable
Bad or missing speedo drive gear(s) in tail shaft housing of the transmission
Defective VSS
Defective ECM
Code 25 - MAT High
Trouble Code 25 indicates that the Manifold Air Temperature (MAT) sensor is reporting abnormally high readings. When the air is hot, the thermistor has a low resistance, which rises as the air temperature cools. High readings indicate a possible bad sensor or short in the MAT circuit.
The conditions for setting this code are:
MAT reading is > 275 deg F (135 deg C), and
The engine has been running for more than 16 seconds, and
The vehicle speed is > 40 MPH
Refer to the Code 23 description for typical sensor resistance values.
Typical causes for this code include:
Defective MAT sensor
MAT signal shorted to ground or to sensor ground
Defective ECM
Code 31 - Wastegate Solenoid Fault
Trouble Code 31 indicates that the Wastegate Solenoid may not be functioning correctly. The wastegate solenoid is controlled by a Pulse Width Modulated (PWM) signal from the ECM. The ECM controls turbo boost by varying the PWM waveform (duty cycle) to the wastegate. The wastegate responds by bleeding off exhaust pressure upstream of the turbine, thus controlling boost pressure.
The conditions for setting this code are:
The ECM is commanding a solenoid duty cycle of between 5% and 94%, and
No electrical feedback is being received from the solenoid, and
The above conditions are met for 2 seconds.
Typical causes for this code include:
TCC/Soleniod fuse blown (in underdash fusebox)
Poor or corroded connections between the ECM and the wastegate solenoid
Open or shorted solenoid
Defective, sticking or misadjustedwastegate linkage
Defective ECM
NOTE: Ensure correct operation of other engine subsystems, including but not limited to the TPS and MAF sensors and check the wastegate actuation hardware.
Code 32 - EGR fail
Trouble Code 32 indicates that the Exhaust Gas Recirculation (EGR) valve diaphragm is not where the ECM expects it to be. The ECM controls the diaphragm with a Pulse-Width Modulated (PWM) waveform. The EGR has a vacuum bleed solenoid that adjusts the vacuum applied to the EGR valve based on this pulse width. If there is sufficient vacuum at the EGR valve, a switch closes to send a signal back to the ECM. The absence of this signal is the bases for code 32.
The conditions for setting this code are:
No vacuum to EGR (switch open), and
Code 33 or 34 (MAF error) is not present, and
Engine running and
LV8 is less than 100, and
Coolant temperature is > 118 deg F (48 deg C), and
The EGR solenoid duty cycle is < 65%, and
The above conditions are met for more than 25 seconds
Typical causes for this code include:
Faulty EGR control solenoid
Faulty connection to EGR control solenoid
Faulty EGR valve-to-ECM connection
Plugged EGR passages and/or sticking EGR valve
Defective EGR valve
Defective ECM
Code 33 - MAF High
Trouble Code 33 indicates that the Mass Air Flow (MAF) sensor is reporting more air is entering the engine than makes sense based on RPM and TPS. The MAF sensor produces a frequency output; around 30 Hz at idle to 150 Hz under acceleration. The frequency varies proportionally to airflow. The ECM monitors the frequency and thus determines airflow into the engine. Typical idle MAF is 5 to 7 grams per second.
The conditions for setting this code are:
No Code 21 or 22 (TPS Error) present, and
The air flow reported is > 40 grams per second, and
TPS indicates < 10% throttle position, and
The engine speed is 1400 RPM or less, and the above conditions exist for over 5 seconds.
Typical causes for this code include:
Faulty MAF sensor
Faulty MAF-to-ECM connection
Exceedingly noisy spark plug wires
Poor routing of MAF harness (i.e. near coil packs)
Misadjusted TPS sensor
Defective MAF sensor
Defective ECM
Code 34 - MAF Low
Trouble Code 34 indicates that the Mass Air Flow (MAF) sensor is reporting less air is entering the engine than makes sense based on RPM and TPS. The MAF sensor produces a frequency output; around 30 Hz at idle to 150 Hz under acceleration. The frequency varies proportionally to airflow. The ECM monitors the frequency and thus determines airflow into the engine. Typical idle MAF is 5 to 7 grams per second.
The conditions for setting this code are:
No Code 21 or 22 (TPS Error) present, and
The air flow reported is < 4 grams per second, and
TPS indicates 10% or more throttle position, and
The engine speed is 1800 RPM or higher, and
The above conditions exist for over 5 seconds.
Typical causes for this code include:
Faulty MAF sensor
Faulty air ducting to or from MAF sensor
Faulty ECM-to-MAF connections
Poor routing of MAF harness (i.e. near coil packs)
Maladjusted TPS sensor
Defective MAF sensor
Defective ECM
Code 33 - MAP High
Trouble Code 33 indicates that the Manifold Absolute Pressure (MAP) sensor is reporting an abnormally high voltage. This indicates low vacuum
The MAP sensor responds to changes in manifold pressure (vacuum). The MAP signal voltage will vary from 1-1.5 volts at closed throttle idle to about 4-4.5 volts at WOT. If the MAP sensor fails, the ECM will substitute a fixed MAP value and use the TPS to control fuel delivery.
The conditions for setting this code are:
MAP signal voltage high
TPS is less than 2%
Condition persists for 5 or more seconds
Typical causes for this code include:
Faulty MAP ensor
Faulty MAP-to-ECM connection
Exceedingly noisy spark plug wires
Poor routing of MAP harness (i.e. near coil packs)
Misadjusted TPS sensor
Very low vaccum (check for hose/intake restriction)
Defective ECM
Code 34 - MAP Low
Trouble Code 34 indicates that the Manifold Absolute Pressure (MAP) sensor is reporting an abnormally low voltage. This indicates high vacuum
The MAP sensor responds to changes in manifold pressure (vacuum). The MAP signal voltage will vary from 1-1.5 volts at closed throttle idle to about 4-4.5 volts at WOT. If the MAP sensor fails, the ECM will substitute a fixed MAP value and use the TPS to control fuel delivery
The conditions for setting this code are:
No Code 21 or 22 (TPS Error) present, and
MAP signal voltage is below 14 kPa
Engine speed is below 1200 rpm
- or -
TPS is greater than 20%
The above conditions exist for over 5 seconds.
Typical causes for this code include:
Faulty MAP sensor
Faulty hose to/from the MAP sensor
Faulty ECM-to-MAP connections
Poor routing of MAP harness (i.e. near coil packs)
Misadjusted TPS sensor
Defective ECM
Code 35 - Idle Speed Error
Trouble Code 35 indicates that the closed throttle engine speed is at least 150 RPM more or less than the commanded idle RPM for 20 seconds.
The conditions for setting this code are:
Idle speed is 150 RPM more or lessthan commanded idle speed
The above conditions exist for over 20 seconds.
Typical causes for this code include:
If the idle speed is too high, look for vacuum leaks or air paths around the IAC
If the idle speed is too low, look for restrictions in the air path, too lean or rich mixtures
Mixture too lean
Mixture too rich
Blockage of the IAC with deposits or "coke"
A/C Compressor or Relay failure
Defective ECM
Code 41 - Cam Sensor Failure
Trouble Code 41 indicates that the Camshaft Sensor is not functioning properly. The ignition module uses the Cam Sensor signal for timing the spark firing. The ignition module also passes this signal to the ECM to enable sequential fuel injection.
The inability to properly determine engine position from the Cam Sensor will generate Code 41. The engine will continue to run if the signal is lost from the sensor, however it will not restart after shut down. If the Cam signal from the ignition module to the ECM is lost while running, the ECM will switch to the batch fuel injection mode. The engine can be re-started but will continue to run in the batch mode as long as the fault is present.
The conditions for setting this code are:
The engine is running, and
The Cam Sensor signal is not received by the ECM in the last 1 second interval
Typical causes for this code include:
Faulty cap on the cam sensor
Loose or misadjusted Cam Sensor
Loose "wheel" on the cam sensor shaft
Defective Cam Sensor-to-ECM connections
Defective ECM
Cam sensor installation and adjustment procedures call for very exact tolerances. It is for this reason that it is recommended that the service manual be consulted while performing any adjustment or replacement of the Camshaft Sensor.
Code 42 - EST Failure
Trouble Code 42 indicates that there may be a malfunction in the Electronic Spark Timing (EST) system. During cranking, the timing is controlled by the ignition module while the ECM monitors the engine speed. When the engine speed exceeds 400 RPM, the ECM sends a BYPASS signal to the ignition module which switches the timing to ECM control. The ECM calculates what the timing should be then "tells" the ignition module via the EST circuit. An open or ground in the EST circuit will stall the engine and set a Code 42. The engine can be re-started but it will run on ignition module timing.
The conditions for setting this code are:
System in BYPASS mode but the ignition module is still controlling timing
- or -
Engine speed > 600 RPM with no EST pulses (ECM controlled timing) going to the ignition module for 200 msec.
Typical causes for this code include:
BYPASS line is open or grounded
EST line is open or grounded
PROM or CALPACK not seated properly in the ECM
Poor connections between ignition module and ECM
Poor routing of EST harness and/or poor quality ignition wires (EMI induced electrical noise)
Faulty or incorrect ignition module
Faulty ECM
Code 43 - ESC Failure
Trouble Code 43 indicates that there may be a malfunction in the Electronic Spark Control (ESC) circuit. ESC is used to sense spark knock (pinging) and retard the timing to eliminate it. A knock sensor (located at the rear of the engine block) sends signals to an ESC module which then signals the ECM that knocking is being detected. The ECM will retard the timing by as much as 20 degrees in 1 degree increments.
A loss of knock sensor signal or loss of ground at the ESC module will cause the signal at the ECM to remain high. The ECM will act as if no knock is present, and may possibly result in engine damage, if there is detonation. Loss of the ESC signal to the ECM will cause the ECM to constantly retard the timing to its maximum. This results in sluggish performance and a Code 43.
The conditions for setting this code are:
Engine is running and
ESC input signal has been low more than 2.23 seconds
Typical causes for this code include:
Open or shorted knock sensor
Loose knock sensor
Excessive mechanical noise within engine
Improper or incorrectly installed PROM or CALPACK in the ECM or defective ECM
Intermittent open in the EST line to the ignition module
Code 44 - O2 Lean
Trouble Code 44 indicates that the O2 sensor is showing a persistently high exhaust oxygen content (lean), despite the efforts of the ECM to increase injector on-time (thus increasing fuel delivered). Integrator and BLM numbers may indicate > 128 by a substantial margin.
The conditions for setting this code are:
No Code 33 or Code 34 (MAF Error) present, and
The O2 sensor voltage remains below 250 mVolts, and
The ECM is in Closed Loop control, and the above conditions exist for more than 50 seconds.
Typical causes for this code include:
O2 sensor defective or lead shorted
Faulty EPROM calibration
Lean injectors (dirty or blocked)
Water in fuel
Exhaust leaks upstream of O2 sensor
Fuel pressure or volume too low
MAF sensor reading lower airflow than is actually present
Vacuum leaks
Incorrect or poorly calibrated PROM
Code 45 - O2 Rich
Trouble Code 45 indicates that the O2 sensor is showing a persistently low exhaust oxygen content (rich), despite the efforts of the ECM to decrease injector on-time (thus decreasing fuel delivered). Integrator and BLM numbers may indicate < 128 by a substantial margin.
The conditions for setting this code are:
No Code 34 or Code 35 (MAF error) present, and
The O2 sensor voltage remains above 752 mV, and
The ECM is in Closed Loop control, and
Throttle position is < 2 percent or > 20 percent, and the above conditions exist for more than 20 seconds.
Typical causes for this code include:
O2 sensor defective or contaminated (if incorrect RTV sealant or too much RTV is used, this may happen)
Faulty EPROM calibration
Leaking fuel injectors
Fuel pressure too high
EMI interference from poor plug wires
Evaporative Emission system defect
TPS and/or EGR problem
MAF sensor reading higher airflow than is actually present
Code 51 - PROM Failure
Trouble Code 51 indicates that the ECM sensed a fault in the PROM. When the PROM was initially created, a checksum number representing the total of all the cell values was also stored. The ECM uses this checksum as one way to determine if the contents of any cell has changed.A Code 51 causes the ECM to enter Back-Up mode which uses the CALPAK for default sensor values.
The conditions for setting this code are:
Power has just been applied to the ECM, and
The calculated checksum does not match the stored checksum.
- or -
The engine was just started, and
Either of two specific PROM locations do not contain the expected value. (One location should have 1's in the odd numbered bits and the other has 1's in the even numbered bit positions.)
Typical causes for this code include:
Incorrectly installed PROM module
Defective PROM module
Defective ECM
Code 52 - CALPACK Fault
Trouble Code 52 indicates that the ECM sensed a fault with the CALPACK. The CALPACK is a plug-in module separate from the PROM, that contains preset calibrations used by the system during "limp home" (backup) mode. The ECM continuously checks for its presence while power is applied.
The conditions for setting this code are:
The ECM does not sense the CALPACK
Typical causes for this code include
Incorrectly installed CALPACK module
Incorrect CALPACK module for this vehicle
Defective or incorrectly inserted PROM
Defective ECM
Code 53 - Water Injection Failure
Trouble Code 53 refers to a feature never actually installed on any Turbo Regal. This code was reserved for when these vehicles where being developed, in the event that water injection hardware would be installed in production vehicles. Since water injection was never actually used, this code should never appear.
Typical causes for this code include:
Incorrect PROM installed in the ECM
PROM incorrectly installed in the ECM
Defective PROM
Some after market PROMs, particularly those designed as 'off road use only', may not properly deal with trouble codes. If it is suspected this is causing a Code 53, contact the PROM manufacturer.
Code 55 - A/D Failure
Trouble Code 55 indicates that the Analog-to-Digital (A/D) converter in the ECM is faulty. This converter reads sensors (e.g., TPS, Oxygen) and coverts their analog voltage output to a digital number for use by the ECM. If the converter fails, the ECM sets this code.
The conditions for setting this code are:
The A/D Converter has failed to properly read a sensor after 24 attempts.
Typical causes for this code include:
Defective or incorrectly inserted PROM
Defective ECM
If replacing the ECM, be sure to transfer both the PROM and the CALPACK from the old unit. If the old ECM also indicated PROM failure (Code 51) or a bad CALPACK (Code 52), be sure to verify these components are fully operational in the new unit. If they are not, they too will have to be replaced.
Code 54 - Fuel Pump Relay Failed
Trouble Code 54 indicates the Fuel Pump Relay has failed.
Typical causes for this code include:
Defective relay
Dirt/water in relay
Wiring fault to relay
Blown fuse/circuit breaker
Defective ECM
In the words of Porky Pig "Th.. tha.th.th.tha.tha..th..tha.that..that.s..that's all folks"
IP: Logged
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11:43 PM
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