Tink
11-02-09, 07:14 PM
CODE 12
Trouble Code 12 is a special case code that is not logged into the ECM's Non-Volatile Memory 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 by flashing 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 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.
NOTE: The codes will not be displayed in order of occurrence but rather in numerical order.
CODE 13
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 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 with no code 21 or 22 (TPS errors) present, coolant temperature at least 118 deg F (48 deg C), O2 sensor voltage not fluctuating (i.e. steady between 350 and 557 mV), TPS signal indicates above idle (over 6%), and all the above conditions met for more than 8 seconds.
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
Trouble Code 14 indicates that the Coolant Temperature Sensor (CTS) is reporting abnormally high readings. 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 for more than 20 seconds.
NOTE: A default temperature of 111 deg F is used while the error is present.
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
Trouble Code 15 indicates that the Coolant Temperature Sensor (CTS) is reporting abnormally low readings. 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 for more than 4 seconds.
NOTE: A default temperature of 111 deg F is used while the error is present.
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
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:
TPS reading is > 4.90 volts
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
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:
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:
- Maladjusted 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 32
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), coolant temperature is > 118 deg F (48 deg C), and the EGR solenoid duty cycle is < 65% for more than 25 seconds.
Typical causes for this code include:
- Faulty EGR valve-to-ECM connection
- Plugged EGR passages and/or sticking EGR valve
- Defective EGR valve
- Defective ECM
CODE 42
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
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:
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
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).
The conditions for setting this code are:
O2 sensor voltage remains below 250 mVolts, and the ECM is in Closed Loop control for more than 50 seconds.
Typical causes for this code include:
- O2 sensor defective or lead shorted
- Lean injectors (dirty or blocked)
- Water in fuel
- Exhaust leaks upstream of O2 sensor
- Fuel pressure or volume too low
- Vacuum leaks
- Incorrect or poorly calibrated PROM
CODE 45
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).
The conditions for setting this code are:
O2 sensor voltage remains above 752 mV, the ECM is in Closed Loop control, and throttle position is < 2 percent or > 20 percent 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)
- Leaking fuel injectors
- Fuel pressure too high
- EMI interference from poor plug wires
- Evaporative Emission system defect
- TPS and/or EGR problem
Trouble Code 12 is a special case code that is not logged into the ECM's Non-Volatile Memory 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 by flashing 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 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.
NOTE: The codes will not be displayed in order of occurrence but rather in numerical order.
CODE 13
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 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 with no code 21 or 22 (TPS errors) present, coolant temperature at least 118 deg F (48 deg C), O2 sensor voltage not fluctuating (i.e. steady between 350 and 557 mV), TPS signal indicates above idle (over 6%), and all the above conditions met for more than 8 seconds.
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
Trouble Code 14 indicates that the Coolant Temperature Sensor (CTS) is reporting abnormally high readings. 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 for more than 20 seconds.
NOTE: A default temperature of 111 deg F is used while the error is present.
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
Trouble Code 15 indicates that the Coolant Temperature Sensor (CTS) is reporting abnormally low readings. 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 for more than 4 seconds.
NOTE: A default temperature of 111 deg F is used while the error is present.
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
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:
TPS reading is > 4.90 volts
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
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:
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:
- Maladjusted 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 32
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), coolant temperature is > 118 deg F (48 deg C), and the EGR solenoid duty cycle is < 65% for more than 25 seconds.
Typical causes for this code include:
- Faulty EGR valve-to-ECM connection
- Plugged EGR passages and/or sticking EGR valve
- Defective EGR valve
- Defective ECM
CODE 42
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
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:
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
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).
The conditions for setting this code are:
O2 sensor voltage remains below 250 mVolts, and the ECM is in Closed Loop control for more than 50 seconds.
Typical causes for this code include:
- O2 sensor defective or lead shorted
- Lean injectors (dirty or blocked)
- Water in fuel
- Exhaust leaks upstream of O2 sensor
- Fuel pressure or volume too low
- Vacuum leaks
- Incorrect or poorly calibrated PROM
CODE 45
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).
The conditions for setting this code are:
O2 sensor voltage remains above 752 mV, the ECM is in Closed Loop control, and throttle position is < 2 percent or > 20 percent 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)
- Leaking fuel injectors
- Fuel pressure too high
- EMI interference from poor plug wires
- Evaporative Emission system defect
- TPS and/or EGR problem