Engine Controls - Self-Diagnostics - 4.0L: Overview — Oldsmobile Aurora II (1999-2003)

Description

Several states require that a vehicle pass On-Board Diagnostic (OBD) system tests and the Inspection/Maintenance (I/M) emission inspection in order to renew license plates. This is accomplished by viewing the I/M system status display on a scan tool. Using a scan tool, the I/M system status can observed in order to verify that the vehicle meets the criteria that complies with local area requirements.

Purpose of this test is to satisfy enable criteria necessary to execute all Inspection/Maintenance (I/M) readiness diagnostics, and to complete the trips (drive cycles) for those particular diagnostics. When all diagnostic tests have been completed, I/M system status indicators are set to YES. Perform this test when more than one or all of the I/M system status indicators are set to NO.

Purpose of this test is to satisfy the enable criteria necessary to execute Inspection/Maintenance (I/M) readiness diagnostics for the Secondary Air Injection (AIR) system. Test may be used to set the I/M system status indicators to YES. Ensure vehicle meets conditions listed in enable criteria before performing procedure. Failure to meet any of the conditions listed may produce inaccurate test results. See ENABLE CRITERIA .

Purpose of this test is to satisfy enable criteria necessary to execute Inspection/Maintenance (I/M) readiness diagnostics for the catalyst system. Test may be used to set I/M system status indicators to YES. Ensure vehicle meets conditions listed in enable criteria before performing procedure. Failure to meet any of the conditions listed may produce inaccurate test results. See ENABLE CRITERIA .

Purpose of this test is to satisfy enable criteria necessary to execute Inspection/Maintenance (I/M) readiness diagnostics for the Exhaust Gas Recirculation (EGR) system. Test may be used to set I/M system status indicators to YES. Ensure vehicle meets conditions listed in enable criteria before performing procedure. Failure to meet any of the conditions listed may produce inaccurate test results. See ENABLE CRITERIA .

Purpose of this test is to satisfy enable criteria necessary to execute Inspection/Maintenance (I/M) readiness diagnostics for the Evaporative Emission (EVAP) system. Test may be used to set I/M system status indicators to YES. Ensure vehicle meets conditions listed in enable criteria before performing procedure. Failure to meet any of the conditions listed may produce inaccurate test results. See ENABLE CRITERIA .

Purpose of this test is to satisfy enable criteria necessary to execute Inspection/Maintenance (I/M) readiness diagnostics for Heated Oxygen Sensor/Oxygen Sensor (HO2S/O2S) system. Test may be used to set I/M system status indicators to YES. Ensure vehicle meets conditions listed in enable criteria before performing procedure. Failure to meet any of the conditions listed may produce inaccurate test results. See ENABLE CRITERIA .

Purpose of this test is to satisfy enable criteria necessary to execute Inspection/Maintenance (I/M) readiness diagnostics for Heated Oxygen Sensor (HO2S) heater system. Test may be used to set I/M system status indicators to YES. Ensure vehicle meets conditions listed in enable criteria before performing procedure. Failure to meet any of the conditions listed may produce inaccurate test results. See ENABLE CRITERIA .

Data Link Connector (DLC) provides operating power for scan tool through terminal No. 16 (Orange wire) and ground through terminal No. 4 (Black wire). DLC provides class 2 serial data signal through terminal No. 2 (Purple wire) and ground through terminal No. 5 (Black/White wire). Scan tool will power up with ignition off.

Heated Oxygen Sensor (HO2S) heater is a device used to reduce the time that it takes for HO2S to go active. The Powertrain Control Module (PCM) uses a high-side driver to apply ignition voltage to bank 1 sensor 1 heater, and a low-side driver Output Driver Module (ODM) to supply ground path. The PCM monitors high-side driver for circuit conditions that are incorrect for commanded state of driver. If PCM detects an improper circuit condition in high-side driver for HO2S bank 1 sensor 1, DTC P0030 will set.

Heated Oxygen Sensor (HO2S) heater is a device used to reduce the time that it takes for HO2S to go active. HO2S bank 1 sensor 2 heater helps maintain proper sensor temperature for catalyst testing and fuel trim adjustments. HO2S heater receives power through a fused ignition circuit. Powertrain Control Module (PCM) uses a low-side driver Output Driver Module (ODM) to turn heater on and off. The PCM monitors the circuit for conditions that are incorrect for commanded state of low-side driver. If PCM detects an incorrect circuit condition for commanded state of low-side driver, DTC P0036 will set.

Mass Airflow (MAF) sensor is an airflow meter that measures the amount of air entering engine. Powertrain Control Module (PCM) uses MAF sensor signal to provide correct fuel delivery for a wide range of engine speeds and loads. A small quantity of air entering the engine indicates deceleration or idle. A large quantity of air entering the engine indicates an acceleration or high load situation. The MAF sensor has an ignition 1 voltage circuit, a ground circuit and a signal circuit. The PCM applies a voltage to MAF sensor on the signal circuit. MAF sensor uses the voltage to produce a frequency based on inlet airflow through the sensor bore. The PCM uses barometric pressure, air density, manifold pressure, throttle position, and engine RPM to calculate a predicted MAF value. The PCM compares actual MAF sensor signal to the predicted MAF value to determine if signal is stuck based on a lack of variation, or is too low, or too high for a given operating condition. Diagnostic Trouble Code (DTC) will set if actual MAF/IAT sensor signal is not within a predetermined range of calculated MAF value.

Mass Airflow (MAF) sensor is an airflow meter that measures the amount of air entering engine. Powertrain Control Module (PCM) uses MAF sensor signal to provide correct fuel delivery for a wide range of engine speeds and loads. A small quantity of air entering engine indicates deceleration or idle. A large quantity of air entering engine indicates an acceleration or high load situation. The MAF sensor has an ignition 1 voltage circuit, ground circuit and a signal circuit. The PCM applies a voltage to MAF sensor on the signal circuit. MAF sensor uses the voltage to produce a frequency based on inlet airflow through the sensor bore. The frequency will vary within a range of about 2000 Hz at idle to about 10,000 Hz at maximum engine load. DTC P0102 will set if PCM detects a frequency signal lower than the possible range of a normally operating MAF/IAT sensor.

Mass Airflow (MAF) sensor is an airflow meter that measures the amount of air entering engine. Powertrain Control Module (PCM) uses the MAF sensor signal to provide correct fuel delivery for a wide range of engine speeds and loads. A small quantity of air entering engine indicates deceleration or idle. A large quantity of air entering engine indicates an acceleration or high load situation. MAF sensor has an ignition 1 voltage circuit, ground circuit and a signal circuit. The PCM applies a voltage to MAF sensor on the signal circuit. MAF sensor uses the voltage to produce a frequency based on inlet airflow through the sensor bore. The frequency will vary within a range of about 2000 Hz at idle to about 10,000 Hz at maximum engine load. DTC P0103 will set if PCM detects a frequency signal higher than the possible range of a normally operating MAF/IAT sensor.

Manifold Absolute Pressure (MAP) sensor responds to pressure changes in intake manifold. The pressure changes occur based on engine load. Powertrain Control Module (PCM) supplies 5 volts to MAP sensor on the 5-volt reference circuit. The PCM also provides a ground on the low reference circuit. The MAP sensor provides a signal to PCM on the signal circuit which is relative to pressure changes in the manifold. The PCM should detect a low signal voltage at a low MAP, such as during idle or deceleration. The PCM should detect a high signal voltage at a high MAP, such as with ignition on or at Wide Open Throttle (WOT). MAP sensor value is also used to determine the Barometric Pressure (BARO). This occurs when ignition is on. The BARO reading may also be updated whenever engine is operated at WOT. The PCM monitors MAP sensor signal for voltage outside of the normal range. The PCM calculates a predicted value for the MAP sensor based on throttle position and engine speed. The PCM then compares the predicted value to the actual MAP sensor signal. DTC P0106 will set if actual MAP sensor signal is not within the predicted range for at least one second.

Manifold Absolute Pressure (MAP) sensor responds to pressure changes in the intake manifold. The pressure changes occur based on engine load. Powertrain Control Module (PCM) supplies 5 volts to the MAP sensor on the 5-volt reference circuit. The PCM also provides a ground on the low reference circuit. The MAP sensor provides a signal to the PCM on the signal circuit which is relative to pressure changes in the manifold. The PCM should detect a low signal voltage at a low MAP, such as during idle or deceleration. The PCM should detect a high signal voltage at a high MAP, such as with ignition on or at Wide Open Throttle (WOT). MAP sensor value is also used to determine the Barometric Pressure (BARO). This occurs when ignition is on. The BARO reading may also be updated whenever the engine is operated at WOT. The PCM monitors the MAP sensor signal for voltage outside of the normal range. DTC P0107 will set if MAP sensor voltage is less than .5 volt for at least 2 seconds.

Manifold Absolute Pressure (MAP) sensor responds to pressure changes in the intake manifold. The pressure changes occur based on engine load. Powertrain Control Module (PCM) supplies 5 volts to MAP sensor on the 5-volt reference circuit. The PCM also provides a ground on the low reference circuit. The MAP sensor provides a signal to the PCM on the signal circuit which is relative to pressure changes in the manifold. The PCM should detect a low signal voltage at a low MAP, such as during idle or deceleration. The PCM should detect a high signal voltage at a high MAP, such as when ignition is on or at a Wide Open Throttle (WOT). MAP sensor value is also used to determine the Barometric Pressure (BARO). This occurs when ignition is on. The BARO reading may also be updated whenever engine is operated at WOT. The PCM monitors the MAP sensor signal for voltage outside of the normal range. DTC P0108 will set when PCM detects MAP sensor signal voltage is excessively high.

Intake Air Temperature (IAT) sensor is a thermistor that measures temperature of air entering the engine. The Powertrain Control Module (PCM) supplies 5 volts to the IAT sensor signal circuit through a pull-up resistor. When intake air is cold, the PCM detects a high voltage on the IAT sensor signal circuit. As the intake air warms, the PCM detects a lower voltage on the IAT sensor signal circuit. The IAT sensor is a thermistor that varies resistance based on temperature. As temperature of sensor increases, resistance decreases. High temperature will result in a low signal voltage. DTC P0112 will set if PCM detects an excessively low IAT sensor signal voltage (high temperature indicated).

Intake Air Temperature (IAT) sensor is a thermistor that measures temperature of air entering the engine. The Powertrain Control Module (PCM) supplies 5 volts to the IAT sensor signal circuit through a pull-up resistor. When intake air is cold, the PCM detects a high voltage on the IAT sensor signal circuit. As intake air warms, the PCM detects a lower voltage on the IAT sensor signal circuit. DTC P0113 will set if PCM detects an excessively high IAT sensor signal voltage (low temperature indicated).

Engine Coolant Temperature (ECT) sensor is a thermistor that measures temperature of engine coolant. The Powertrain Control Module (PCM) supplies 5 volts to the ECT sensor signal circuit through a pull-up resistor. When engine coolant temperature is cold, ECT sensor resistance is high. When engine coolant temperature increases, ECT sensor resistance decreases. With high sensor resistance, the PCM detects a high voltage on the ECT sensor signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the ECT sensor signal circuit. DTC P0117 will set if PCM detects an excessively low ECT sensor signal voltage, indicating a high temperature.

Engine Coolant Temperature (ECT) sensor is a thermistor that measures temperature of the engine coolant. The Powertrain Control Module (PCM) supplies 5 volts to the ECT sensor signal circuit through a pull-up resistor. When engine coolant temperature is cold, ECT sensor resistance is high. When engine coolant temperature increases, ECT sensor resistance decreases. With high sensor resistance, the PCM detects a high voltage on the ECT sensor signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the ECT sensor signal circuit. DTC P0118 will set if PCM detects an excessively high ECT sensor signal voltage, indicating a low temperature.

Throttle Position (TP) sensor is used by the Powertrain Control Module (PCM) to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with 3 circuits, a 5-volt reference circuit, a low reference circuit, and a signal circuit. The PCM provides TP sensor with a 5-volt reference circuit and a low reference circuit. Rotation of the TP sensor rotor from closed throttle position to Wide Open Throttle (WOT) position provides PCM with a signal voltage from less than one volt to more than 4 volts through the TP sensor signal circuit. When conditions for running this DTC are met, the PCM will use the Manifold Absolute Pressure (MAP) sensor to determine if the predicted operating range of the TP Sensor is correct. A skewed MAP sensor may cause DTC P0121 to set and should be tested for proper operation if the TP sensor is determined to be operating properly and this DTC continues to set.

Throttle Position (TP) sensor is used by the Powertrain Control Module (PCM) to determine throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with 3 circuits, a 5-volt reference circuit, a low reference circuit, and a signal circuit. The PCM provides TP sensor with a 5-volt reference circuit and a low reference circuit. Rotation of the TP sensor rotor from closed throttle position to Wide Open Throttle (WOT) position provides PCM with a signal voltage from less than one volt to more than 4 volts through the TP sensor signal circuit. DTC P0122 will set if PCM detects an excessively low signal voltage.

Throttle Position (TP) sensor is used by the Powertrain Control Module (PCM) to determine throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with 3 circuits, a 5-volt reference circuit, a low reference circuit, and a signal circuit. The PCM provides TP sensor with a 5-volt reference circuit and a low reference circuit. Rotation of the TP sensor rotor from closed throttle position to Wide Open Throttle (WOT) position provides the PCM with a signal voltage from less than one volt to more than 4 volts through TP sensor signal circuit. DTC P0123 will set if PCM detects an excessively high signal voltage.

Engine Coolant Temperature (ECT) sensor monitors temperature of coolant. This input is used by the Powertrain Control Module (PCM) for engine control and as an enabling criteria for some diagnostics. If engine coolant temperature does not increase normally or does not reach regulating temperature of thermostat, diagnostics that use the ECT as an enabling criteria may not run when expected. DTC P0125 will set if an excessive amount of time passes before engine coolant temperature reaches closed loop operation temperature of 154°F (68°C).

Heated Oxygen Sensor (HO2S) is used to detect oxygen content in the exhaust. The Powertrain Control Module (PCM) supplies HO2S with a signal circuit and a ground circuit. The PCM supplies a bias voltage between the circuits. The HO2S varies voltage based on oxygen content in the exhaust. When exhaust stream is lean (more oxygen), HO2S produces a low voltage signal. When exhaust stream is rich (less oxygen), HO2S produces a high voltage signal. The PCM monitors HO2S signal during closed loop. To correct for rich or lean conditions, PCM adjusts injector pulse width. DTC P0131 will set if HO2S bank 1 sensor 1 signal voltage remains less than 75 millivolts for about 50 seconds during normal closed loop fuel control. DTC will also set if HO2S bank 1 sensor 1 signal voltage remains at less than 575 millivolts during power enrichment fuel control.

Heated Oxygen Sensor (HO2S) is used to detect oxygen content in the exhaust. The Powertrain Control Module (PCM) supplies HO2S with a signal circuit and a ground circuit. The PCM supplies a bias voltage between the circuits. The HO2S varies voltage based on oxygen content in the exhaust. When exhaust stream is lean (more oxygen), HO2S produces a low voltage signal. When exhaust stream is rich (less oxygen), HO2S produces a high voltage signal. The PCM monitors the HO2S signal during closed loop. To correct for rich or lean conditions, PCM adjusts injector pulse width. DTC P0132 will set if HO2S bank 1 sensor 1 signal voltage remains more than 900 millivolts for about 50 seconds during normal closed loop fuel control. DTC will also set if HO2S bank 1 sensor 1 signal voltage remains at more than 200 millivolts during deceleration fuel control.

Heated Oxygen Sensor (HO2S) heater is used to reduce the time that it takes for HO2S to go active. The Powertrain Control Module (PCM) controls HO2S heaters using a high-side driver, 2 low-side drivers, and a current monitoring driver. The current monitoring driver tests condition of the heaters. The high-side driver provides HO2S bank 1 sensor 1 heater with ignition voltage. A fused ignition feed provides HO2S bank 1 sensor 2, and bank 2 sensor 1 with ignition voltage. HO2S receives ground through one of the low-side drivers. With engine running, PCM turns on the high-side, and the low-side drivers to warm-up the oxygen sensors. When proper conditions are present, the PCM keeps high-side driver on, turns on the current monitor driver, and then turns off the warm-up driver. This allows the PCM to record a total current value for both of the fuel control heaters. If test conditions remain stable, the PCM enters second stage of the test. During this stage, the PCM keeps the current monitor on, and turns off the high-side driver. This allows the PCM to record a current value for bank 2 sensor 1 heater circuit. The PCM subtracts the bank 2 sensor 1 current value from the total current value to determine the current value for bank 1 sensor 1. DTC P0135 will set if PCM detects HO2S bank 1 sensor 1 current value is outside of calibrated range.

Heated Oxygen Sensor (HO2S) heater is used to reduce time that it takes for HO2S to go active. HO2S bank 1 sensor 2 heater helps to maintain sensor at proper temperature for catalyst testing, and additional adjustments to fuel trim. The HO2S heater receives power through a fused ignition circuit. The Powertrain Control Module (PCM) turns sensor heater on and off using a low-side driver output driver module located within PCM. The PCM only tests the heater after a cold start. PCM determines a cold start based on difference between Engine Coolant Temperature (ECT) at last key off, and ECT at current key on. When HO2S voltage indicates a sufficiently active sensor, PCM looks at how much time has elapsed since start-up. DTC P0141 set if PCM determines that too much time was required for sensor to become active.

Heated Oxygen Sensor (HO2S) is used to detect oxygen content in the exhaust. The Powertrain Control Module (PCM) supplies HO2S with a signal circuit and a ground circuit. The PCM supplies a bias voltage between the circuits. The HO2S varies voltage based on oxygen content in the exhaust. When exhaust stream is lean (more oxygen), HO2S produces a low voltage signal. When exhaust stream is rich (less oxygen), HO2S produces a high voltage signal. The PCM monitors the HO2S signal during closed loop. To correct for rich or lean conditions, PCM adjusts injector pulse width. DTC P0151 will set if HO2S bank 2 sensor 1 signal voltage remains less than 75 millivolts for about 50 seconds during normal closed loop fuel control. DTC will also set if HO2S bank 1 sensor 1 signal voltage remains at less than 575 millivolts during power enrichment fuel control.

Heated Oxygen Sensor (HO2S) is used to detect oxygen content in the exhaust. The Powertrain Control Module (PCM) supplies HO2S with a signal circuit and a ground circuit. The PCM supplies a bias voltage between the circuits. The HO2S varies voltage based on oxygen content in the exhaust. When exhaust stream is lean (more oxygen), HO2S produces a low voltage signal. When exhaust stream is rich (less oxygen), HO2S produces a high voltage signal. The PCM monitors the HO2S signal during closed loop. To correct for rich or lean conditions, PCM adjusts injector pulse width. DTC P0152 will set if HO2S bank 2 sensor 1 signal voltage remains more than 900 millivolts for about 50 seconds during normal closed loop fuel control. DTC will also set if HO2S bank 2 sensor 1 signal voltage remains at more than 200 millivolts during deceleration fuel control. DTC will set if HO2S bank 2 sensor 1 signal voltage remains more than 900 millivolts for about 50 seconds during normal closed loop fuel control. DTC will also set if HO2S bank 2 sensor 1 signal voltage remains at more than 200 millivolts during deceleration fuel control.

Heated Oxygen Sensor (HO2S) heater is used to reduce time that it takes for HO2S to go active. The Powertrain Control Module (PCM) controls HO2S heaters using a high-side driver, 2 low-side drivers, and a current monitoring driver. The current monitoring driver tests the condition of the heaters. The high-side driver provides HO2S bank 1 sensor 1 heater with ignition voltage. A fused ignition feed provides HO2S bank 1 sensor 2, and bank 2 sensor 1 with ignition voltage. HO2S receives ground through one of the low-side drivers. With engine running, PCM turns on the high-side, and the low-side drivers to warm-up oxygen sensors. When proper conditions are present, the PCM keeps the high-side driver on, turns on the current monitor driver, and then turns off the warm-up driver. This allows the PCM to record a total current value for both of the fuel control heaters. If test conditions remain stable, the PCM enters the second stage of the test. During this stage, the PCM keeps the current monitor on, and turns off the high-side driver. This allows PCM to record a current value for bank 2 sensor 1 heater circuit. PCM subtracts bank 2 sensor 1 current value from total current value to determine current value for bank 1 sensor 1. DTC P0155 will set if PCM detects HO2S bank 2 sensor 1 current value is outside of calibrated range.

Powertrain Control Module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy and emission control. Fuel delivery is controlled differently during open loop and closed loop. During open loop the PCM determines fuel delivery based on sensor signals, without oxygen sensor input. During closed loop the PCM adds oxygen sensor inputs to calculate short term and long term fuel trim (fuel delivery adjustments). If oxygen sensors indicate a lean condition, fuel trim values will be more than zero percent. If oxygen sensors indicate a rich condition, fuel trim values will be less than zero percent. Short term fuel trim values change rapidly in response to Heated Oxygen Sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. DTC P0171 will set if PCM detects an excessively lean condition.

Powertrain Control Module (PCM) controls air/fuel metering system in order to provide best possible combination of driveability, fuel economy and emission control. Fuel delivery is controlled differently during open loop and closed loop. During open loop the PCM determines fuel delivery based on sensor signals, without oxygen sensor input. During closed loop the PCM adds oxygen sensor inputs to calculate short term and long term fuel trim (fuel delivery adjustments). If oxygen sensors indicate a lean condition, fuel trim values will be more than zero percent. If oxygen sensors indicate a rich condition, fuel trim values will be less than zero percent. Short term fuel trim values change rapidly in response to Heated Oxygen Sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. Fuel trim diagnostic will conduct a test to determine if a rich condition actually exists or if excessive vapor from EVAP canister is causing a rich condition. DTC P0172 will set if PCM detects an excessively rich condition.

Powertrain Control Module (PCM) controls air/fuel metering system in order to provide best possible combination of driveability, fuel economy and emission control. Fuel delivery is controlled differently during open loop and closed loop. During open loop the PCM determines fuel delivery based on sensor signals, without oxygen sensor input. During closed loop the PCM adds oxygen sensor inputs to calculate short term and long term fuel trim (fuel delivery adjustments). If oxygen sensors indicate a lean condition, fuel trim values will be more than zero percent. If oxygen sensors indicate a rich condition, fuel trim values will be less than zero percent. Short term fuel trim values change rapidly in response to Heated Oxygen Sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. DTC P0174 will set if PCM detects an excessively lean condition.

Powertrain Control Module (PCM) controls air/fuel metering system in order to provide best possible combination of driveability, fuel economy and emission control. Fuel delivery is controlled differently during open loop and closed loop. During open loop the PCM determines fuel delivery based on sensor signals, without oxygen sensor input. During closed loop the PCM adds oxygen sensor inputs to calculate short term and long term fuel trim (fuel delivery adjustments). If oxygen sensors indicate a lean condition, fuel trim values will be more than zero percent. If oxygen sensors indicate a rich condition, fuel trim values will be less than zero percent. Short term fuel trim values change rapidly in response to Heated Oxygen Sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. Fuel trim diagnostic will conduct a test to determine if a rich condition actually exists or if excessive vapor from EVAP canister is causing a rich condition. DTC P0175 will set if PCM detects an excessively rich condition.

Powertrain Control Module (PCM) enables appropriate fuel injector on intake stroke for each cylinder. Ignition voltage is supplied to fuel injectors. The PCM controls each fuel injector by grounding the control circuit via a solid state device called a driver. The PCM monitors driver state. DTC P0201-P0208 will set if PCM detects an incorrect voltage on fuel injector control circuit.

Powertrain Control Module (PCM) provides ignition voltage to coil side of fuel pump relay. When ignition is first turned on, PCM energizes fuel pump relay, which applies power to fuel pump. The PCM enables fuel pump relay as long as engine is cranking or running, and crankshaft reference pulses are received. If no crankshaft reference pulses are received, PCM de-energizes fuel pump relay after 2 seconds. The PCM monitors voltage on fuel pump relay control circuit. Diagnostic Trouble Code (DTC) will set if PCM detects an incorrect voltage on fuel injector control circuit.

Powertrain Control Module (PCM) uses information from Crankshaft Position (CKP) sensors and Camshaft Position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring variations in crankshaft rotation speed for each cylinder, the PCM is able to detect individual misfire events. A misfire rate that is high enough can cause catalytic converter damage. Malfunction indicator light will flash on and off when conditions for catalytic converter damage are present. DTC P0300 will sets if PCM detects a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emission levels to exceed mandated standard.

Powertrain Control Module (PCM) uses a knock sensor to detect engine detonation, or spark knock. Knock sensor produces an AC signal at all engine speeds and loads. The PCM makes adjustments to spark timing based on the amplitude and frequency of knock sensor signal. The PCM uses the knock sensor to calculate amount of normal engine noise (a noise channel) for a wide range of engine speeds and loads. The PCM compares actual knock sensor signal to learned noise channel. DTC P0325 will set if PCM detects a malfunction in the integrated knock sensor diagnostic circuity that will not allow proper diagnosis of knock sensor system.

Powertrain Control Module (PCM) uses a knock sensor to detect engine detonation, or spark knock. Knock sensor produces an AC signal at all engine speeds and loads. The PCM makes adjustments to spark timing based on the amplitude and frequency of knock sensor signal. The PCM uses knock sensor to calculate amount of normal engine noise (a noise channel) for a wide range of engine speeds and loads. The PCM compares actual knock sensor signal to learned noise channel. DTC P0326 will set when knock sensor voltage and variation is not within normally expected ranges for more than 4 seconds.

Powertrain Control Module (PCM) uses a knock sensor to detect engine detonation, or spark knock. Knock sensor produces an AC signal at all engine speeds and loads. The PCM makes adjustments to spark timing based on the amplitude and frequency of knock sensor signal. The PCM uses knock sensor to calculate amount of normal engine noise (a noise channel) for a wide range of engine speeds and loads. The PCM compares actual knock sensor signal to learned noise channel. DTC P0327 will set if PCM detects a knock sensor signal of less than .4 volt.

Powertrain Control Module (PCM) uses dual Crankshaft Position (CKP "A" and CKP "B") sensors to determine crankshaft position. The PCM supplies an ignition voltage and a ground for each sensor. During engine rotation, a slotted ring, machined into the crankshaft, causes CKP sensors to return a series of on and off pulses to the PCM. The PCM uses these pulses to decode position of crankshaft. The PCM uses 2 basic methods of decoding engine position: angle based and time based (using either CKP "A" or CKP "B" sensor input). During normal operation, the PCM uses the angle based method. In order to operate in this mode, PCM must receive signal pulses from both CKP sensors. The PCM uses the signal pulses to determine an initial crankshaft position, and to generate 24X reference and 4X reference signals. Once initial crankshaft position is determined, the PCM continuously monitors both sensors for valid signal inputs. As long as both signal inputs remain, the PCM will continue to use the angle based mode. When either CKP signal is lost, the PCM will compare the 24X reference signal to the Camshaft Position (CMP) sensor signal. If PCM detects a valid CMP signal, and the 24X reference to CMP signal correlation is correct, the PCM determines that CKP sensor "A" is at fault. However, if the 24X reference to CMP correlation is incorrect, the PCM determines that CKP sensor "B" is at fault. If PCM determines that CKP sensor "A" is at fault, DTC P0335 will set. The PCM will switch from angle based mode to time based mode "B" using CKP sensor "B" signal input.

Powertrain Control Module (PCM) uses dual Crankshaft Position (CKP "A" and CKP "B") sensors to determine crankshaft position. The PCM supplies an ignition voltage and a ground for each sensor. During engine rotation, a slotted ring, machined into the crankshaft, causes CKP sensors to return a series of on and off pulses to the PCM. The PCM uses these pulses to decode position of crankshaft. The PCM uses 2 basic methods of decoding engine position: angle based and time based (using either CKP "A" or CKP "B" sensor input). During normal operation, the PCM uses the angle based method. In order to operate in this mode, PCM must receive signal pulses from both CKP sensors. The PCM uses the signal pulses to determine an initial crankshaft position, and to generate 24X reference and 4X reference signals. Once initial crankshaft position is determined, the PCM continuously monitors both sensors for valid signal inputs. As long as both signal inputs remain, the PCM will continue to use the angle based mode. When either CKP signal is lost, the PCM will compare the 24X reference signal to the Camshaft Position (CMP) sensor signal. If PCM detects a valid CMP signal, and the 24X reference to CMP signal correlation is correct, the PCM determines that CKP sensor "A" is at fault. However, if the 24X reference to CMP correlation is incorrect, the PCM determines that CKP sensor "B" is at fault. If PCM determines that CKP sensor "B" is at fault, DTC P0385 will set. The PCM will switch from angle based mode to time based "A" mode using CKP sensor "A" signal input. If after switching to time based "A" mode PCM detects an intermittent loss of CKP sensor "A" signal, DTC P0336 will set.

Powertrain Control Module (PCM) uses Camshaft Position (CMP) sensor high resolution signal to determine position of valve train in relation to engine cylinders. The PCM uses CMP high resolution signal to sequence the ignition system and fuel injectors. The PCM supplies a 12-volt reference and a low reference to the CMP sensor. The CMP sensor returns a signal pulse in response to the reluctor track, located on camshaft sprocket. If during operation, the PCM detects a loss of CMP sensor high resolution signal, DTC P0340 will set.

Powertrain Control Module (PCM) uses the Camshaft Position (CMP) sensor high resolution signal to determine position of valve train in relation to engine cylinders. The PCM uses CMP high resolution signal to sequence the ignition system and fuel injectors. The PCM supplies a 12-volt reference and a low reference to the CMP sensor. The CMP sensor returns a signal pulse in response to the reluctor track, located on the camshaft sprocket. If during operation, the PCM detects an incorrect correlation between CMP signal and CKP signal, DTC P0341 will set.

An individual ignition coil is used for each cylinder. There are 2 separate Ignition Control Module (ICM) assemblies located on valve cover for each cylinder bank. Each ICM assembly contains an ignition module and 4 coils, which connects directly to spark plug using a boot. The ICM receives power from a fused ignition feed circuit. PCM uses the individual IC circuits to control coil sequencing and spark timing for each cylinder. DTC P0351 will set if PCM detects a short to ground in IC circuit.

An individual ignition coil is used for each cylinder. There are 2 separate Ignition Control Module (ICM) assemblies located on valve cover for each cylinder bank. Each ICM assembly contains an ignition module and 4 coils, which connects directly to spark plug using a boot. The ICM receives power from a fused ignition feed circuit. PCM uses the individual IC circuits to control coil sequencing and spark timing for each cylinder. DTC P0352 will set if PCM detects a short to ground in IC circuit.

An individual ignition coil is used for each cylinder. There are 2 separate Ignition Control Module (ICM) assemblies located on valve cover for each cylinder bank. Each ICM assembly contains an ignition module and 4 coils, which connects directly to spark plug using a boot. The ICM receives power from a fused ignition feed circuit. PCM uses the individual IC circuits to control coil sequencing and spark timing for each cylinder. DTC P0353 will set if PCM detects a short to ground in IC circuit.

An individual ignition coil is used for each cylinder. There are 2 separate Ignition Control Module (ICM) assemblies located on valve cover for each cylinder bank. Each ICM assembly contains an ignition module and 4 coils, which connects directly to spark plug using a boot. The ICM receives power from a fused ignition feed circuit. PCM uses the individual IC circuits to control coil sequencing and spark timing for each cylinder. DTC P0354 will set if PCM detects a short to ground in IC circuit.

An individual ignition coil is used for each cylinder. There are 2 separate Ignition Control Module (ICM) assemblies located on valve cover for each cylinder bank. Each ICM assembly contains an ignition module and 4 coils, which connects directly to spark plug using a boot. The ICM receives power from a fused ignition feed circuit. PCM uses the individual IC circuits to control coil sequencing and spark timing for each cylinder. DTC P0355 will set if PCM detects a short to ground in IC circuit.

An individual ignition coil is used for each cylinder. There are 2 separate Ignition Control Module (ICM) assemblies located on valve cover for each cylinder bank. Each ICM assembly contains an ignition module and 4 coils, which connects directly to spark plug using a boot. The ICM receives power from a fused ignition feed circuit. PCM uses the individual IC circuits to control coil sequencing and spark timing for each cylinder. DTC P0356 will set if PCM detects a short to ground in IC circuit.

An individual ignition coil is used for each cylinder. There are 2 separate Ignition Control Module (ICM) assemblies located on valve cover for each cylinder bank. Each ICM assembly contains an ignition module and 4 coils, which connects directly to spark plug using a boot. The ICM receives power from a fused ignition feed circuit. PCM uses the individual IC circuits to control coil sequencing and spark timing for each cylinder. DTC P0357 will set if PCM detects a short to ground in IC circuit.

An individual ignition coil is used for each cylinder. There are 2 separate Ignition Control Module (ICM) assemblies located on valve cover for each cylinder bank. Each ICM assembly contains an ignition module and 4 coils, which connects directly to spark plug using a boot. The ICM receives power from a fused ignition feed circuit. PCM uses the individual IC circuits to control coil sequencing and spark timing for each cylinder. DTC P0358 will set if PCM detects a short to ground in IC circuit.

Powertrain Control Module (PCM) uses dual Crankshaft Position (CKP "A" and CKP "B") sensors to determine crankshaft position. The PCM supplies an ignition voltage and a ground for each sensor. During engine rotation, a slotted ring, machined into the crankshaft, causes CKP sensors to return a series of on and off pulses to the PCM. The PCM uses these pulses to decode position of crankshaft. The PCM uses 2 basic methods of decoding engine position: angle based and time based (using either CKP "A" or CKP "B" sensor input). During normal operation, the PCM uses the angle based method. In order to operate in this mode, PCM must receive signal pulses from both CKP sensors. The PCM uses the signal pulses to determine an initial crankshaft position, and to generate 24X reference and 4X reference signals. Once initial crankshaft position is determined, the PCM continuously monitors both sensors for valid signal inputs. As long as both signal inputs remain, the PCM will continue to use the angle based mode. When either CKP signal is lost, the PCM will compare the 24X reference signal to the Camshaft Position (CMP) sensor signal. If PCM detects a valid CMP signal, and the 24X reference to CMP signal correlation is correct, the PCM determines that CKP sensor "A" is at fault. However, if the 24X reference to CMP correlation is incorrect, the PCM determines that CKP sensor "B" is at fault. If PCM determines that CKP sensor "B" is at fault, DTC P0385 will set. The PCM will switch from angle based mode to time based "A" mode using CKP sensor "A" signal input.

Powertrain Control Module (PCM) tests Exhaust Gas Recirculation (EGR) system during deceleration by momentarily commanding EGR valve open while monitoring Manifold Absolute Pressure (MAP) sensor signal. When EGR valve is opened, the PCM should see a proportional increase in MAP. If expected increase in MAP is not seen, PCM notes amount of error that was detected and adjusts an internal failure counter toward a failure threshold level. When failure counter exceeds failure threshold level, PCM will set DTC P0401.

Powertrain Control Module (PCM) monitors Exhaust Gas Recirculation (EGR) valve pintle position input to ensure valve responds properly to PCM commands. The linear EGR valve is controlled by using an ignition positive driver and ground circuit within the PCM. The driver has the ability to detect an electrical malfunction in the EGR solenoid high control circuit or EGR low control circuit. If an electrical malfunction occurs, the driver signals the PCM to set DTC P0403.

Powertrain Control Module (PCM) monitors Exhaust Gas Recirculation (EGR) valve pintle position input to ensure valve responds properly to PCM commands. The PCM compares EGR position sensor with desired EGR position when valve is commanded open. If difference between EGR position sensor and desired EGR position is more than 8 percent, DTC P0404 will set.

Powertrain Control Module (PCM) monitors Exhaust Gas Recirculation (EGR) valve pintle position input to ensure valve responds properly to commands from PCM, and to detect a fault if EGR valve position signal circuit is open or shorted. If PCM detects an excessively low EGR valve position signal voltage, DTC P0405 will set.

Powertrain Control Module (PCM) uses AIR relays to control both AIR pumps. PCM also controls AIR vacuum control solenoid valve that supplies vacuum to AIR shutoff valves. When AIR system is inactive, the AIR shutoff valves prevent airflow in either direction. When AIR system is active, the PCM applies ground to one of the AIR relays and to the vacuum control solenoid valve. After a few seconds, the PCM applies ground to the other AIR relay. Fresh airflows from the pumps, through the system hoses, past the shutoff valves, and into the exhaust stream. The air helps the catalyst to quickly reach a working temperature, lowering tail pipe emissions during start-up. The PCM runs a passive test and an active test in order to diagnose the AIR system. Both tests involve a response from the fuel control Heated Oxygen Sensors (HO2S) bank 1 sensor 1, and HO2S bank 2 sensor 1. If both passive tests pass, the PCM takes no further action. If either part of the passive test fails or is inconclusive, the PCM initiates the active tests. If PCM determines that HO2S voltages did not respond as expected during the tests, DTC P0410 will set.

The Secondary Air Injection (AIR) pump lowers tail pipe emissions during start-up. The AIR system consists of AIR pump, shutoff valves, AIR solenoid, system hoses and pipes, AIR relay, fuses, and related wiring. The Powertrain Control Module (PCM) uses the AIR relay to control the AIR pump. The PCM also controls the AIR solenoid valve that supplies vacuum to the AIR shutoff valves. With AIR system inactive, the AIR shutoff valves prevent airflow in either direction. With AIR system active, the PCM applies ground to the AIR relay and to the AIR solenoid. Fresh airflows from the pump, through the system hoses, past the shutoff valves, and into the exhaust stream. The air helps the catalyst to quickly get to a working temperature, lowering tail pipe emissions during a start-up. The PCM runs a passive test and an active test in order to diagnose the AIR system. Both tests involve a response from the fuel control Heated Oxygen Sensor (HO2S) bank 1 sensor 1, and HO2S bank 2 sensor 1. If both passive tests pass, the PCM takes no further action. If either part of the passive test fails or is inconclusive, the PCM initiates the active tests. If PCM determines that HO2S voltages did not respond as expected during the tests, DTC P0410 will set.

Powertrain Control Module (PCM) uses the Output Driver Modules (ODM) to control many functions of the engine and transaxle. The ODMs supply the ground path for the PCM-controlled device when the PCM commands the device on. Each ODM can control several outputs. Unlike quad driver modules used in earlier model years, the ODMs are able to diagnose each output circuit. The PCM monitors ODMs for circuit conditions that are incorrect for the commanded state of the ODM. If PCM detects an improper circuit condition in the ODM that controls the AIR vacuum control solenoid valve, DTC P0412 will set.

Powertrain Control Module (PCM) tests the ability of catalytic converter to lower exhaust emissions. The PCM determines catalytic converter performance by calculating oxygen storage capacity. The PCM calculates this data by comparing oxygen content of exhaust entering catalytic converter, read from front and rear Heated Oxygen Sensors (HO2S), to exhaust leaving catalytic converter read from the post HO2S.

Catalytic converter efficiency test is performed in 2 stages. The first stage calculates post-converter oxygen sensor deviations (difference from the average value), compares these deviations to the maximum allowable deviation (based on airflow), and records a failure if those deviations are excessive. The second stage is only run if the first stage fails or DTC P0420 is currently set. The second stage averages the difference between the deviations calculated in the first stage and the maximum allowable deviations. If the second stage average is too high, DTC P0420 will set.

Evaporative Emission (EVAP) large leak test applies vacuum to EVAP system and monitors vacuum decay. The Powertrain Control Module (PCM) monitors Fuel Tank Pressure (FTP) sensor signal to determine vacuum decay rate. At an appropriate time, the PCM turns EVAP canister purge valve on (open) and EVAP canister vent valve on (closed). This allows engine to draw a vacuum on EVAP system. At a calibrated time, or vacuum level, the PCM turns purge valve off (closed), sealing the system, and monitors FTP sensor input to determine EVAP system vacuum. If system is unable to achieve calibrated vacuum level, or if vacuum level decreases too rapidly, DTC P0440 will set.

The state of EVAP switch is monitored by the PCM to determine if EVAP solenoid is open and passing vacuum. The PCM accomplishes this by monitoring amount of time EVAP switch is continuously open or closed during purge. The test conditions met, PCM starts a timer, which will be reset when the switch transitions from open to closed or vice versa. If switch remains closed for 9 seconds continuously, DTC P0440 will set. If switch remains open for 2 seconds continuously, test is passed.

This DTC tests Evaporative Emission (EVAP) system for a small leak. Powertrain Control Module (PCM) monitors Fuel Tank Pressure (FTP) sensor signal to determine vacuum decay rate. At an appropriate time, PCM turns EVAP canister purge valve and EVAP canister vent valve on. This allows engine to draw a vacuum on EVAP system. At a calibrated time, or vacuum level, PCM turns EVAP canister purge valve off, sealing the system, and monitors FTP sensor input to determine EVAP system vacuum decay. If PCM detects a leak larger than calibrated amount, DTC P0442 will set.

An ignition voltage is supplied directly to Evaporative Emission (EVAP) canister purge valve. EVAP canister purge valve is pulse width modulated. Powertrain Control Module (PCM) controls EVAP canister purge valve "ON" time by grounding the control circuit via an internal switch called a driver. San tool displays amount of "ON" time as a percentage. The PCM monitors driver status. If PCM detects an incorrect voltage for the commanded state of the driver, DTC P0443 will set.

This DTC tests Evaporative Emission (EVAP) system for a restricted or blocked EVAP vent path. Powertrain Control Module (PCM) commands EVAP canister purge valve and EVAP canister vent valve on. This allows a vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the PCM commands EVAP canister purge valve and EVAP canister vent valve off. The PCM monitors Fuel Tank Pressure (FTP) sensor for a decrease in vacuum. If vacuum does not decrease to near zero in. H2O in a calibrated time, DTC P0446 will set.

An ignition voltage is supplied directly to Evaporative Emission (EVAP) canister vent valve. Powertrain Control Module (PCM) controls EVAP vent valve by grounding control circuit via an internal switch called a driver. Primary function of the driver is to supply ground for the controlled component. The PCM monitors driver status. If PCM detects an incorrect voltage for commanded state of the driver, DTC P0449 will set.

Fuel Tank Pressure (FTP) sensor measures the difference between air pressure or vacuum in the Evaporative Emission (EVAP) system, and outside air pressure. The Powertrain Control Module (PCM) supplies a 5-volt reference and a low reference circuit to FTP sensor. The FTP sensor signal circuit voltage varies depending on EVAP system pressure or vacuum. If PCM detects FTP sensor signal voltage goes to less than calibrated value, DTC P0452 will set.

Fuel Tank Pressure (FTP) sensor measures the difference between air pressure or vacuum in the Evaporative Emission (EVAP) system, and outside air pressure. The Powertrain Control Module (PCM) supplies a 5-volt reference and a low reference circuit to the FTP sensor. The FTP sensor signal circuit voltage varies depending on EVAP system pressure or vacuum. If PCM detects FTP sensor signal voltage goes to more than calibrated value, DTC P0453 will set.

Idle Air Control (IAC) valve is located on throttle body. It consists of a movable pintle, driven by a gear attached to an electric motor called a stepper motor. The IAC valve motor is a 2 phase bi-polar permanent magnet stepper motor that is capable of highly accurate rotation, or movement, every time polarity of a winding is changed. Polarity can be seen when observing a test light connected between ground or B+ and an IAC valve circuit while the Powertrain Control Module (PCM) is attempting to change engine RPM (test light will flash on or off each time polarity is changed). The PCM does not use a physical sensor to determine IAC pintle position, but uses a predicted number of counts, one count represents one change in polarity which equals one step of the stepper motor. The PCM counts the steps it has commanded to determine IAC pintle position. The PCM uses IAC valve to control engine idle speed. It does this by changing pintle position in the idle air passage of the throttle body. This varies airflow around throttle plate when throttle is closed. To determine desired position of IAC pintle at idle or during deceleration, the PCM refers to the following inputs: engine RPM, battery voltage, air temperature, engine coolant temperature, throttle position sensor angle, engine load, and vehicle speed. When ignition is turned off after an ignition cycle, the PCM will first seat the IAC pintle in the air by-pass bore, and then retract it a predetermined amount of counts to allow proper amount of air to by-pass throttle plate for engine start-up. This procedure is known as an IAC reset.

Powertrain Control Module (PCM) monitors the high-side refrigerant pressure via the A/C refrigerant pressure sensor. The PCM applies a 5-volt reference and a low reference to the sensor. Changes in the A/C refrigerant pressure cause the A/C refrigerant pressure input to the PCM to vary. When pressure is high, signal voltage is high. When pressure is low, signal voltage is low. When the pressure is high the PCM commands the cooling fans on. When the pressure is too high or low the PCM will not allow the A/C compressor clutch to engage. When the DTC is set, the PCM does not allow the A/C compressor clutch to engage. This is done to protect the compressor. The PCM sends the A/C pressure data to the Dash Integration Module (DIM) over the class 2 communication line. DTC P0532 will set when PCM detects an A/C signal voltage that is excessively low.

Powertrain Control Module (PCM) monitors system voltage to make sure that voltage stays within the proper range. Damage to components and incorrect data input can occur when voltage is out of range. PCM monitors system voltage over an extended length of time. If PCM detects a system voltage out of an expected range for the calibrated length of time, DTC P0560 will set.

Powertrain Control Module (PCM) monitors system voltage to make sure that voltage stays within the proper range. Damage to components and incorrect data input can occur when voltage is out of range. PCM monitors system voltage over an extended length of time. If PCM detects an excessively low system voltage, DTC P0562 will set.

Powertrain Control Module (PCM) monitors system voltage to make sure that voltage stays within the proper range. Damage to components and incorrect data input can occur when voltage is out of range. PCM monitors system voltage over an extended length of time. If PCM detects an excessively high system voltage, DTC P0563 will set.

Powertrain Control Module (PCM) uses an Electrically Erasable Programmable Read Only Memory (EEPROM) to store software and calibration information. PCM uses a checksum to verify integrity of the information. At time of programming, PCM calculates a checksum and stores the value in the EEPROM. With ignition on, PCM retrieves the information and performs a checsum. PCM compares the ignition on value to the value stored in the EEPROM. If checksum at ignition on does not match stored checksum, DTC P0601 will set.

Powertrain Control Module (PCM) uses an Electrically Erasable Programmable Read Only Memory (EEPROM) to store software and calibration information. EEPROM is not replaceable, PCM must be replaced. Replacement PCM does not contain final program information. Replacement PCM must be programed. If replacement PCM is not programmed, DTC P0602 will set. When DTC sets, PCM disables fuel pump relay and fuel injectors.

Powertrain Control Module (PCM) performs the checksum test in order to monitor integrity of the non-volatile information across the ignition cycles. The PCM uses an Electrically Erasable Programmable Read-Only Memory (EEPROM) to store this information at key off. Before storing the information, the PCM calculates a checksum then stores the value along with the information. At key on, the PCM retrieves the information from the EEPROM and places the information in the Random Access Memory (RAM). After retrieval, the PCM conducts a checksum of the information in RAM and compares this value to the value that is stored in the EEPROM at the previous key off. If the checksums do not match, Diagnostic Trouble Code (DTC) P0603 will set. Also, during operation, the PCM maintains a checksum on a certain section of the RAM that contains critical information. If at any time this running checksum fails, DTC P0603 will set.

Powertrain Control Module (PCM) copies program information that is stored in the Electrically Erasable Programmable Read Only Memory (EEPROM) to the Random Access Memory (RAM). This allows PCM to work with, and update the information. PCM tests all areas of the RAM. If PCM detects an error in any area of the RAM, DTC P0604 will set.

Powertrain Control Module (PCM) is capable of diagnosing a malfunction within the controller. If PCM detects a malfunction within the controller, DTC P0606 will set.

Powertrain Control Module (PCM) uses Output Driver Modules (ODM) to control many functions of the engine and transaxle. The ODMs supply the ground path for the PCM-controlled device when the PCM commands the device on. Each ODM can control several outputs. Unlike quad driver modules used in earlier model years, the ODMs are able to diagnose each output circuit. The PCM monitors ODMs for circuit conditions that are incorrect for the commanded state of the ODM. If PCM detects an improper circuit condition in the ODM that controls the Malfunction Indicator Light (MIL), DTC P0650 will set.

Manifold Absolute Pressure (MAP) sensor responds to pressure changes in the intake manifold. The pressure changes occur based on engine load. Powertrain Control Module (PCM) supplies 5 volts to MAP sensor on the 5-volt reference circuit. The PCM also provides a ground on the low reference circuit. The MAP sensor provides a signal to the PCM on the signal circuit which is relative to pressure changes in the manifold. The PCM should detect a low signal voltage at a low MAP, such as during idle or deceleration. The PCM should detect a high signal voltage at a high MAP, such as when ignition is on or at a Wide Open Throttle (WOT). MAP sensor value is also used to determine the Barometric Pressure (BARO). This occurs when ignition is on. The BARO reading may also be updated whenever engine is operated at WOT. The PCM monitors MAP sensor signal for voltage outside of the normal range. DTC P1106 will set when PCM detects MAP sensor signal voltage is intermittently high.

Manifold Absolute Pressure (MAP) sensor responds to pressure changes in the intake manifold. The pressure changes occur based on engine load. Powertrain Control Module (PCM) supplies 5 volts to MAP sensor on the 5-volt reference circuit. The PCM also provides a ground on the low reference circuit. The MAP sensor provides a signal to the PCM on the signal circuit which is relative to pressure changes in the manifold. The PCM should detect a low signal voltage at a low MAP, such as during idle or deceleration. The PCM should detect a high signal voltage at a high MAP, such as when ignition is on or at a Wide Open Throttle (WOT). MAP sensor value is also used to determine the Barometric Pressure (BARO). This occurs when ignition is on. The BARO reading may also be updated whenever engine is operated at WOT. The PCM monitors MAP sensor signal for voltage outside of the normal range. DTC P1107 will set when PCM detects MAP sensor signal voltage is intermittently low.

Intake Air Temperature (IAT) sensor is a thermistor that measures temperature of air entering the engine. The Powertrain Control Module (PCM) supplies 5 volts to the IAT sensor signal circuit through a pull-up resistor. When intake air is cold, the PCM detects a high voltage on IAT sensor signal circuit. As intake air warms, the PCM detects a lower voltage on IAT sensor signal circuit. DTC P1111 will set if PCM detects an intermittently high IAT sensor signal voltage (low temperature indicated).

Intake Air Temperature (IAT) sensor is a thermistor that measures temperature of air entering the engine. The Powertrain Control Module (PCM) supplies 5 volts to the IAT sensor signal circuit through a pull-up resistor. When intake air is cold, the PCM detects a high voltage on IAT sensor signal circuit. As intake air warms, the PCM detects a lower voltage on IAT sensor signal circuit. DTC P1112 will set if PCM detects an intermittently low IAT sensor signal voltage (high temperature indicated).

Engine Coolant Temperature (ECT) sensor is a thermistor that measures temperature of engine coolant. Powertrain Control Module (PCM) supplies 5 volts to ECT sensor signal circuit through a pull-up resistor. When ECT is cold, sensor resistance is high. When ECT increases, sensor resistance lowers. With high sensor resistance, the PCM detects a high voltage on the ECT sensor signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the ECT sensor signal circuit. DTC P1114 will set if PCM detects an intermittently low ECT sensor signal voltage (high temperature indicated).

Engine Coolant Temperature (ECT) sensor is a thermistor that measures temperature of engine coolant. Powertrain Control Module (PCM) supplies 5 volts to ECT sensor signal circuit through a pull-up resistor. When ECT is cold, sensor resistance is high. When ECT increases, sensor resistance lowers. With high sensor resistance, the PCM detects a high voltage on the ECT sensor signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the ECT sensor signal circuit. DTC P1115 will set if PCM detects an intermittently high ECT sensor signal voltage (low temperature indicated).

Throttle Position (TP) sensor is used by the Powertrain Control Module (PCM) to determine throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with 3 circuits, a 5-volt reference circuit, a low reference circuit, and a signal circuit. The PCM provides TP sensor with a 5-volt reference circuit and a low reference circuit. Rotation of the TP sensor rotor from closed throttle position to Wide Open Throttle (WOT) position provides the PCM with a signal voltage from less than one volt to more than 4 volts through TP sensor signal circuit. DTC P1121 will set if PCM detects an intermittent excessively high signal voltage.

Throttle Position (TP) sensor is used by the Powertrain Control Module (PCM) to determine throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with 3 circuits, a 5-volt reference circuit, a low reference circuit, and a signal circuit. The PCM provides TP sensor with a 5-volt reference circuit and a low reference circuit. Rotation of the TP sensor rotor from closed throttle position to wide open throttle (WOT) position provides the PCM with a signal voltage from less than one volt to more than 4 volts through TP sensor signal circuit. DTC P1122 will set if PCM detects an intermittent excessively low signal voltage.

Heated Oxygen Sensor (HO2S) is used to detect oxygen content in the exhaust. The Powertrain Control Module (PCM) supplies HO2S with a signal circuit and a ground circuit. The PCM supplies a bias voltage between the circuits. The HO2S varies voltage based on oxygen content in the exhaust. When exhaust stream is lean (more oxygen), HO2S produces a low voltage signal. When exhaust stream is rich (less oxygen), HO2S produces a high voltage signal. The PCM monitors HO2S activity to determine a time ratio for lean-to-rich switches, and for rich-to-lean switches. The PCM counts number of lean-to-rich and rich-to-lean switches for 100 seconds. The PCM records time required to complete all transitions. With this information, PCM determines an average transition time for lean-to-rich switches and for rich-to-lean switches.

Powertrain Control Module (PCM) has the ability to disable 4 injectors during an engine over temperature (overheating) condition. Engine is considered over temperature whenever ECT reaches 268°F (131°C). This protection mode allows PCM to alternate between groups of cylinders, thereby reducing coolant temperature. This is accomplished by disabling the fuel injectors. This DTC is set to show that an overheating condition was or is observed by the PCM and that the protection mode has been engaged.

Crankshaft Position (CKP) system variation learning feature is used to calculate the reference period errors that are caused by slight tolerance variations in crankshaft, and in CKP sensors. Calculated error allows the Powertrain Control Module (PCM) to accurately compensate for reference period variations. This procedure enhances the ability of the PCM to detect misfire events over a wider range of engine speed and load conditions. PCM stores CKP system variation values after a learn procedure has been performed. DTC P1336 indicates CKP system variation values have not been stored in the PCM, and CKP system variation learn procedure must be performed. CKP system variation learn procedure must be performed any time the following service procedures are performed, regardless if DTC P1336 is set or not

PCM replacement.
PCM reprogrammed.
Engine replacement.
Crankshaft replacement.
CKP sensor replacement.
Any engine repairs which disturbs crankshaft to crankshaft position sensor relationship.

Vehicle is equipped with 2 separate ignition module assemblies. One assembly for each bank of cylinders. Each assembly contains an Ignition Control Module (ICM) and 4 ignition coils. Each ICM consists of an ignition 1 voltage circuit, ground circuit, IC timing low reference circuit and IC control circuits for cylinders 1-8. DTC P1359 will set if during PCM power-up, PCM detects an open or short to voltage in IC circuit group for cylinders No. 1, 4, 6 and 7 cylinders.

Vehicle is equipped with 2 separate ignition module assemblies. One assembly for each bank of cylinders. Each assembly contains an Ignition Control Module (ICM) and 4 ignition coils. Each ICM consists of an ignition 1 voltage circuit, ground circuit, IC timing low reference circuit and IC control circuits for cylinders 1-8. DTC P1360 will set if during PCM power-up, PCM detects an open or short to voltage in IC circuit group for cylinders No. 2, 3, 5 and 8 cylinders.

Powertrain Control Module (PCM) uses dual Crankshaft Position (CKP "A" and CKP "B") sensors to determine crankshaft position. PCM supplies an ignition voltage and a ground for each sensor. During engine rotation, a slotted ring, machined into the crankshaft, causes CKP sensors to return a series of on and off pulses to the PCM. The PCM uses these pulses to decode position of crankshaft. The PCM uses 2 basic methods of decoding engine position: angle based and time based (using either CKP "A" or CKP "B" sensor input). During normal operation, the PCM uses the angle based method. In order to operate in this mode, PCM must receive signal pulses from both CKP sensors. The PCM uses the signal pulses to determine an initial crankshaft position, and to generate 24X reference and 4X reference signals. Once initial crankshaft position is determined, the PCM continuously monitors both sensors for valid signal inputs. As long as both signal inputs remain, the PCM will continue to use the angle based mode. When either CKP signal is lost, the PCM will compare the 24X reference signal to the Camshaft Position (CMP) sensor signal. If PCM detects a valid CMP signal, and the 24X reference to CMP signal correlation is correct, the PCM determines that CKP sensor "A" is at fault. However, if the 24X reference to CMP correlation is incorrect, the PCM determines that CKP sensor "B" is at fault. If, while in angle-based mode PCM detects an intermittent loss of either CKP signal, DTC P1372.

Rough roads cause torque on the tires that is transmitted to the powertrain. This condition slows down the crankshaft, giving the appearance of a misfire. Electronic Brake and Traction Control Module (EBTCM) determines rough road surfaces using input from wheel speed sensors. EBTCM then sends rough road data to the Powertrain Control Module (PCM) via class 2 serial data. PCM uses rough road data to enhance misfire diagnostics. This data allows PCM to distinguish crankshaft speed variations causes by rough road surfaces from variations caused by true misfires. If EBTCM is unable to identify rough road conditions when PCM detects a misfire condition, DTC P1380 will set.

Rough roads cause torque on the tires that is transmitted to the powertrain. This condition slows down the crankshaft, giving the appearance of a misfire. Electronic Brake and Traction Control Module (EBTCM) determines rough road surfaces using input from wheel speed sensors. EBTCM then sends rough road data to the Powertrain Control Module (PCM) via class 2 serial data. PCM uses rough road data to enhance misfire diagnostics. This data allows PCM to distinguish crankshaft speed variations causes by rough road surfaces from variations caused by true misfires. If a loss of communication occurs that causes PCM not to receive rough road information when a misfire condition is requesting Malfunction Indicator Light (MIL) on, DTC P1381 will set.

The Powertrain Control Module (PCM) monitors Exhaust Gas Recirculation (EGR) valve pintle position input to ensure valve responds properly to PCM commands. When ignition is turned on, the PCM learns the EGR learned minimum position. PCM compares this position to EGR position sensor when EGR valve is commanded closed. If EGR position sensor indicates EGR valve is still open when PCM is commanding EGR valve closed, DTC P1404 will set.

The Secondary Air Injection (AIR) pump lowers tailpipe emissions during start-up. The AIR system consists of AIR pump, shutoff valves, AIR solenoid, system hoses and pipes, AIR relay, fuses, and related wiring. The Powertrain Control Module (PCM) uses the AIR relay to control the AIR pump. The PCM also controls the AIR solenoid that supplies vacuum to the AIR shutoff valves. With AIR system inactive, the AIR shutoff valves prevent airflow in either direction. With AIR system active, the PCM applies ground to the AIR relay and to the AIR solenoid. Fresh airflows from the pump, through the system hoses, past the shutoff valves, and into the exhaust stream. The air helps the catalyst to quickly get to a working temperature, lowering tail pipe emissions during a start-up. The PCM runs a passive test and an active test in order to diagnose the AIR system. Both tests involve a response from the fuel control Heated Oxygen Sensor (HO2S) bank 1 sensor 1, and HO2S bank 2 sensor 1. If both passive tests pass, the PCM takes no further action. If either part of the passive test fails or is inconclusive, the PCM initiates the active tests. If PCM determines that HO2S voltages did not respond as expected during the tests, DTC P1415 will set.

The Secondary Air Injection (AIR) pump(s) lowers tailpipe emissions during start-up. The AIR system consists of AIR pump(s), shutoff valves, AIR solenoid, system hoses and pipes, AIR relay(s), fuses, and related wiring. The Powertrain Control Module (PCM) uses the AIR relay(s) to control the AIR pump(s). The PCM also controls the AIR solenoid that supplies vacuum to the AIR shutoff valves. With AIR system inactive, the AIR shutoff valves prevent airflow in either direction. With AIR system active, the PCM applies ground to the AIR relay and to the AIR solenoid. Fresh airflows from the pump(s), through the system hoses, past the shutoff valves, and into the exhaust stream. The air helps the catalyst to quickly get to a working temperature, lowering tail pipe emissions during a start-up. The PCM runs a passive test and an active test in order to diagnose the AIR system. Both tests involve a response from the fuel control Heated Oxygen Sensor (HO2S) bank 1 sensor 1, and HO2S bank 2 sensor 1. If both passive tests pass, the PCM takes no further action. If either part of the passive test fails or is inconclusive, the PCM initiates the active tests. If PCM determines that HO2S voltages did not respond as expected during the tests, DTC P1416 will set.

This DTC tests for undesired intake manifold vacuum flow to Evaporative Emission (EVAP) system. The Powertrain Control Module (PCM) seals the EVAP system by commanding EVAP canister purge valve off and EVAP canister vent valve on. The PCM monitors Fuel Tank Pressure (FTP) sensor to determine if a vacuum is being drawn on the EVAP system. If vacuum in the EVAP system is more than a predetermined value within a predetermined time, DTC P1441 will set.

Dash Integration Module (DIM) monitors the A/C low-side refrigerant temperature via the A/C refrigerant low temperature sensor. When the refrigerant is cold, the sensor resistance and signal voltage are high. When the refrigerant is warm, the sensor resistance and signal voltage are low. The DIM will not request A/C compressor clutch engagement when the refrigerant temperature is low enough to cause the A/C evaporator core to freeze.

Engine Coolant Temperature (ECT) sensor is a thermistor. The Powertrain Control Module (PCM) determines the temperature of the engine coolant based on voltage from the ECT sensor. When ECT sensor is cold, resistance and voltage are high. When ECT sensor is warm, resistance and voltage are low. The PCM sends the coolant temperature data to the Dash Integration Module (DIM) over the Class 2 communication line. The DIM will not request A/C compressor clutch engagement if engine coolant temperature is too high. If PCM determines that a fault is present in the ECT sensor signal circuit it will set DTC P0117 or P0118 and substitute a default coolant temperature value. This value is then sent from the PCM to the DIM over the Class 2 communication line. DTC P1536 will set if engine coolant temperature is 250°F (121°C) or more for 2 seconds.

Powertrain Control Module (PCM) monitors the high-side refrigerant pressure via the A/C refrigerant pressure sensor. The PCM applies a 5-volt reference and a low reference to the sensor. Changes in the A/C refrigerant pressure cause the A/C refrigerant pressure input to the PCM to vary. When pressure is high, signal voltage is high. When pressure is low, signal voltage is low. When the pressure is high the PCM commands the cooling fans on. When the pressure is too high or low the PCM will not allow the A/C compressor clutch to engage. When the DTC P1540 is set, the PCM does not allow the A/C compressor clutch to engage. This is done to protect the compressor. The PCM sends the A/C pressure data to the Dash Integration Module (DIM) over the class 2 communication line. DTC will set if A/C pressure is too high.

This test functions on the assumption that a sudden decrease in non-drive wheel speed must be caused by a brake application. Non-drive wheel speed and brakelight switch status are supplied to the PCM through the serial data from the Electronic Brake and Traction Control Module (EBTCM). If there is a 6 MPH or greater decrease of non-drive wheel speed in .4 second and a transition of the Torque Converter Clutch (TCC) or extended travel contacts of the TCC brake switch occurs without a transition of the stoplight switch, DTC P1575 will set.

Powertrain Control Module (PCM) checks the integrity of the non-volatile memory area of the Electrically Erasable Programmable Read-Only Memory (EEPROM). The PCM uses the EEPROM to store the information at key off. There are several locations where the information is stored within the non-volatile memory. If PCM detects a problem in one location of the EEPROM, the PCM will attempt to store the data in another location. If PCM runs out of valid places to store the information, DTC P1621 will set.

The customer-snapshot feature lets customer store the Powertrain Control Module (PCM) data when a driveability problem occurs. This feature permits several snapshots during each ignition cycle. When customer requests the snapshot, PCM stores the data, and sets DTC P1624. The PCM also illuminates the malfunction indicator light for a specific length of time to tell the customer that the data has been stored.

Powertrain Control Module (PCM) uses the 5-volt reference 1 circuit as a sensor feed to the Throttle Position (TP) sensor, Manifold Absolute Pressure (MAP) sensor and Exhaust Gas Recirculation (EGR) position sensor. The PCM monitors voltage on the 5-volt reference 1 circuit. If the voltage is out of tolerance, DTC P1635 will set.

Powertrain Control Module (PCM) uses the 5-volt reference 2 circuit as a sensor feed to the A/C pressure sensor and Fuel Tank Pressure (FTP) sensor. The PCM monitors voltage on the 5-volt reference 2 circuit. If the voltage is out of tolerance, DTC P1639 will set.

Engine Controls - Self-Diagnostics - 4.0L: Overview Oldsmobile Aurora II

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