Engine Controls - Self-Diagnostics - 2.2L: Diagnosis Isuzu Rodeo II

DIAGNOSTIC TROUBLE CODE DEFINITIONS

If any DTCs not listed are displayed by a scan tool, scan tool data may be faulty. Notify scan tool manufacturer of any DTCs displayed that are not included in DTC IDENTIFICATION table.

DTC IDENTIFICATION

SELF-DIAGNOSTIC SYSTEM

Note. If PCM requires replacement, it must be reprogrammed using TECH II or other OBD-II compatible scan tool. Some models may require additional equipment to program EEPROM.

Note. See PIN VOLTAGE CHARTS and WIRING DIAGRAMS articles for PCM harness connector, wire terminal and wire color identification.

Note. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm impedance unless stated otherwise in test procedure.

DIAGNOSTIC TESTS

Note. Diagnostic tests were written specifically for use with TECH II scan tool. Other scan tools can be used, but may have limited functions. To identify circuits and wire colors referenced in testing, see WIRING DIAGRAMS article.

Circuit Description

Engine load is determined using a "speed density" method. This method is calculated using inputs from Manifold Absolute Pressure (MAP) sensor, Crankshaft Position (CKP) sensor, Intake Air Temperature (IAT) sensor and engine RPM. MAP sensor is main sensor used to calculate engine load. PCM supplies a 5-volt reference signal and a ground circuit to MAP sensor. As manifold pressure changes, MAP sensor input voltage to PCM varies from less than 2 volts at idle to greater than 4 volts at Wide Open Throttle (WOT). If PCM detects MAP sensor input voltage that is excessively low, DTC P0106 will be set.

Conditions required to set DTC are

1. No ECT, CKP, EGR, EVAP, MAP, injector, misfire, A/D multiplexer or TP sensor DTCs present.
2. ECT is greater than 14°F (-10°C).
3. EGR flow rate is steady, changing less than 2 percent.
4. Engine speed is steady between 1000-4000 RPM, and changing less than 20 RPM.
5. IAC valve counts are steady, changing less than 3 counts.
6. TP sensor position does not vary more than 5 percent.
7. No status change in brake switch, A/C clutch or power steering pressure switch.
8. MAP value varies more than 10 kPa, for a total of 10 seconds within a 20-second time sample.

Diagnostic Aids

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal connection. Inspect wiring harness for damage. Move connectors and wiring harnesses related to sensor, while observing MAP display on scan tool. A change in display will indicate location of fault. If DTC cannot be duplicated, FAILURE RECORDS data can be used in determining vehicle mileage since DTC was last set. If it is determined that DTC occurs intermittently, performing DTC P1106: MAP SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE or DTC P1107: MAP SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE may isolate cause of fault.

Diagnostic Procedures

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. With ignition on and engine off, review and record FAILURE RECORDS data on scan tool, then clear DTCs. Operate vehicle within conditions noted in FAILURE RECORDS data. Monitor specified DTC information. If scan tool indicates DTC P0106 RAN AND PASSED, go to next step. If scan tool does not indicate DTC P0106 RAN AND PASSED, go to step 4.
3. Check for following conditions: vacuum hoses disconnected, damaged or incorrectly routed, intake manifold vacuum leaks, throttle body leaks, and EGR valve flange and pipe leaks. Repair as necessary. Retest system. If no problem is found, see «DIAGNOSTIC AIDS»(ref-12126-S30773619572000121100000).
4. Disconnect MAP sensor connector and observe MAP value displayed on scan tool. Normal reading is zero volts and 10.3 kPa. If reading is as specified, go to step 6. If reading is not as specified, go to next step.
5. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Using DVOM, check for short to voltage in MAP sensor input circuit (Gray wire) between MAP sensor connector and PCM harness connector terminal F8. see scheme 1and (Scheme 3). If voltage is present, locate short to voltage and repair as necessary. If no voltage is present, go to step 12.
6. Turn ignition off. Disconnect PCM harness connectors. Using DVOM, check MAP sensor input circuit (Gray wire) between MAP sensor connector and PCM harness connector terminal F8 for open circuit or short to ground. see scheme 1and (Scheme 3). Repair as necessary. If no problem was found, go to next step.
7. Connect PCM harness connectors. Turn ignition on. Check MAP sensor connector 5-volt reference terminal (Gray/Red wire) for voltage. If reading indicates about 5 volts, go to next step. If reading does not indicate about 5 volts, locate and repair open or shorted condition in 5-volt reference circuit.
8. Turn ignition off. Using fused jumper wire, connect Gray/Red and Gray wires together at MAP sensor harness connector. Turn ignition on. Observe MAP value displayed on scan tool. If reading is about 5 volts and 104 kPa, go to next step. If reading is not as specified, go to step 12.
9. Turn ignition off. Disconnect PCM harness connectors. Check for open or short to voltage in MAP sensor ground circuit (Gray/Black wire) between MAP sensor connector and PCM harness connector terminal D9. see scheme 1and (Scheme 3). Repair as necessary. If no problem was found, go to next step.
10. Connect PCM harness connectors. Connect DVOM positive lead to MAP sensor connector Gray/Red wire (5-volt reference), and negative lead to MAP sensor connector Gray/Black wire (ground). Turn ignition on. If reading indicates about 5 volts, go to next step. If reading does not indicate about 5 volts, go to step 12.
11. Replace MAP sensor. Retest system.
12. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Scheme 3

Engine load is determined using a "speed density" method. This method is calculated using inputs from Manifold Absolute Pressure (MAP) sensor, Crankshaft Position (CKP) sensor and Intake Air Temperature (IAT) sensor. MAP sensor is main sensor used to calculate engine load. It is also used to determine manifold pressure changes during EGR flow test diagnosis, and to determine vacuum level during other diagnostic functions. If PCM detects a MAP sensor input voltage that is excessively low, DTC P0107 will be set.

Conditions required to set DTC are

1. No TP sensor DTCs present.
2. Engine is running.
3. Throttle angle is greater than zero percent if engine speed is 1300 RPM or less.
4. Throttle angle is greater than 5 percent if engine speed is greater than 1300 RPM.
5. MAP sensor indicates manifold absolute pressure less than 11 kPa.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Move connectors and wiring harnesses related to sensor, while observing MAP display on scan tool. A change in display will indicate location of fault. If DTC cannot be duplicated, FAILURE RECORDS data can be used in determining vehicle mileage since DTC was last set. If it is determined that DTC occurs intermittently, performing DTC P1107: MAP SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE may isolate cause of fault.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. With throttle closed, observe MAP value on scan tool. If MAP value indicates zero volts and 10.3 kPa (at sea level), go to step 4. If MAP value does not indicate zero volts and 10.3 kPa, go to next step.
3. With ignition on and engine off, review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions specified. Monitor specified DTC information. If scan tool indicates DTC P0107 failed, go to next step. If scan tool does not indicate DTC P0107 failed, see «DIAGNOSTIC AIDS»(ref-12126-S35239962592000121100000).
4. Turn ignition off. Disconnect MAP sensor. Using a fused jumper wire, connect MAP sensor harness connector Gray/Red and Gray wires together. (Scheme 3) Turn ignition on. Observe MAP value displayed on scan tool. If reading is about 5 volts and 104 kPa, go to step 10. If reading is not as specified, go to next step.
5. Remove jumper wire from MAP sensor harness connector Gray/Red wire. Reconnect it at PCM harness connector terminal B1 (Gray/Red wire). see scheme 1 Observe MAP value displayed on scan tool. If reading is about 5 volts and 104 kPa, go to next step. If reading is not as specified, go to step 8.
6. Turn ignition off. Disconnect PCM harness connectors. Check for an open circuit or short to ground in Gray/Red wire between PCM harness connector terminal B1 and MAP sensor harness connector. see scheme 1and (Scheme 3). Repair as necessary. If no problem was found, go to next step.
7. Inspect PCM harness connector terminals for damage or poor connection. Repair as necessary. If terminals are okay, go to step 11.
8. Turn ignition off. Disconnect PCM harness connectors. Using a DVOM, check for an open circuit or short to ground in Gray wire between MAP sensor harness connector and PCM harness connector terminal F8. see scheme 1and (Scheme 3). Repair as necessary. If no problem was found, go to next step.
9. Inspect MAP sensor and PCM harness connectors for damaged terminals or poor terminal connection. Repair as necessary and retest system. If no problem was found, go to step 11.
10. Replace MAP sensor and retest system.
11. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Engine load is determined using a "speed density" method. This method is calculated using inputs from Manifold Absolute Pressure (MAP) sensor, Crankshaft Position (CKP) sensor, Intake Air Temperature (IAT) sensor and engine RPM. MAP sensor is main sensor used to calculate engine load. PCM supplies a 5-volt reference signal and a ground circuit to MAP sensor. If PCM detects a MAP sensor input voltage that is excessively high, DTC P0108 will be set.

Conditions required to set DTC are

1. No TP sensor DTCs present.
2. Engine is running.
3. Throttle position is less than 2.7 percent if engine speed is less than 1000 RPM.
4. Throttle position is less than 10 percent if engine speed is greater than 1000 RPM.
5. MAP sensor indicates manifold absolute pressure greater than 90 kPa for specified period of time.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Move connectors and wiring harnesses related to sensor display on scan tool. A change in display may indicate location of fault. If DTC cannot be duplicated, FAILURE RECORDS data can be used in determining vehicle mileage since DTC was last set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step. NOTE: If engine idle is rough, unstable or incorrect, repair idle problem before proceeding.
2. With engine idling, note MAP value on scan tool display. If MAP value reading is more than 4 volts and 90 kPa, go to step 4. If MAP value reading is not more than about 4 volts and 90 kPa, go to next step.
3. With ignition on and engine off, review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions specified. Monitor specified DTC information. If scan tool indicates DTC P0108 failed during this ignition cycle, go to next step. If scan tool does not indicate DTC P0108 failed, see «DIAGNOSTIC AIDS»(ref-12126-S36854148862000121100000).
4. Turn ignition off. Disconnect MAP sensor. Turn ignition on. Observe MAP value displayed on scan tool. If reading is about zero volts and 10.3 kPa, go to next step. If reading is not zero volts and 10.3 kPa, go to step 6.
5. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Using a DVOM, check MAP sensor input circuit (Gray wire) for short to voltage between MAP sensor connector and PCM harness connector terminal F8. see scheme 1and (Scheme 3). If voltage is indicated, locate and repair short to voltage in MAP sensor input circuit and retest system. If voltage is not indicated, go to step 12.
6. Turn ignition off. Disconnect PCM harness connectors. Using a DVOM, check MAP sensor input circuit (Gray wire) between MAP sensor harness connector and PCM harness connector terminal F8 for open circuit or short to ground. see scheme 1and (Scheme 3). Repair as necessary. If no problem was found, go to next step.
7. Connect PCM harness connectors. Turn ignition on. Check for faulty circuit between MAP sensor harness connector Gray/Red wire (5-volt reference) and PCM harness connector terminal B1. Repair as necessary. If no problem was found, go to next step.
8. Turn ignition off. Disconnect MAP sensor. Using a fused jumper wire, connect MAP sensor harness connector Gray/Red and Gray wires together. Turn ignition on. Observe MAP value displayed on scan tool. If reading is about 5 volts and 104 kPa, go to next step. If reading is not as specified, go to step 12.
9. Turn ignition off. Disconnect PCM harness connectors. Check for faulty circuit in MAP sensor Gray/Black wire between MAP sensor harness connector and PCM harness connector terminal D9. see scheme 1and (Scheme 3). Repair as necessary. If no problem was found, go to next step.
10. Connect PCM harness connectors. Connect DVOM between MAP sensor harness connector Gray/Red wire and Gray/Black wire. Turn ignition on. If reading indicates about 5 volts, go to next step. If reading does not indicate about 5 volts, go to step 12.
11. Replace MAP sensor. Retest system.
12. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Intake Air Temperature (IAT) sensor is a thermistor, which varies resistance based on temperature. As temperature of sensor increases, resistance decreases. High temperature will result in a low signal voltage. DTC will set when PCM senses IAT sensor voltage is excessively low (shorted to ground).

Conditions required to set DTC are

1. Vehicle driven at 30 MPH or more.
2. Engine running more than 2 minutes.
3. IAT voltage is less than .10 volts for 12.5 seconds over a 25-second period.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Move connectors and wiring harnesses related to sensor, while observing IAT display on scan tool. A change in display will indicate location of fault. If DTC cannot be duplicated, FAILURE RECORDS data can be used in determining vehicle mileage since DTC was last set. Check for IAT sensor out of range. See IAT SENSOR RESISTANCE table.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. Using scan tool, read Intake Air Temperature (IAT) value. If temperature is more than 283°F (148°C), go to step 4. If temperature is 283°F (148°C) or less, go to next step.
3. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, monitor specified DTC parameters. If scan tool displays DTC P0112 FAILED THIS IGN, test IAT sensor. Using a DVOM, measure resistance across IAT sensor terminals. See «IAT SENSOR RESISTANCE»(ref-12126-S31017588202000121100000) table. Replace IAT sensor if resistance is not as specified. If scan tool does not display DTC P0112 FAILED THIS IGN, go to «DIAGNOSTIC AIDS»(ref-12126-S42193724582000121100000). IAT SENSOR RESISTANCE Temperature °F (°C) Ohms 212° (100°) 177 176° (80°) 332 140° (60°) 667 113° (45°) 1188 95° (35°) 1802 77° (25°) 2796 59° (15°) 4450 41° (5°) 7280 23° (-5°) 12,300 5° (-15°) 21,450 -22° (-30°) 52,700 -40° (-40°) 100,700
4. Turn ignition off. Disconnect IAT sensor harness connector. Turn ignition on. Using scan tool, read IAT value. If reading is less than -36°F (-38°C), go to step 6. If reading is -36°F (-38°C) or more, go to next step.
5. Turn ignition off. Disconnect PCM harness connectors. Check for short to ground in Yellow/Green wire between PCM harness connector terminal B8 and IAT sensor. see scheme 1and (Scheme 4). Repair as necessary. If no problem was found, go to step 7.
6. Replace IAT sensor. Retest system.
7. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Scheme 4

Intake Air Temperature (IAT) sensor is a thermistor, which varies resistance based on temperature. As temperature of sensor increases, resistance decreases. Low temperature will result in a high signal voltage. DTC will set when PCM senses IAT sensor voltage is greater than 5 volts.

Conditions required to set DTC are

1. Engine running for more than 4 minutes.
2. Vehicle speed is less than 20 MPH.
3. MAF value is less than 20 grams per second.
4. ECT signal temperature is greater than 140°F (60°C).
5. IAT signal voltage indicates an intake air temperature less than -38°F (-39°C) for 12.5 seconds over a 25-second period.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Move connectors and wiring harnesses related to sensor, while observing IAT display on scan tool. A change in display will indicate location of fault. If DTC cannot be duplicated, FAILURE RECORDS data can be used in determining vehicle mileage since DTC was last set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. Using scan tool, read IAT value. If temperature reading is less than 5 volts, -36°F (-38°C), go to step 4. If temperature reading is more than specified, go to next step.
3. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, monitor specified DTC parameters. If scan tool displays DTC P0113 FAILED THIS IGN, test IAT sensor. Using a DVOM, measure resistance across sensor terminals. See «IAT SENSOR RESISTANCE»(ref-12126-S31017588202000121100000) table. Replace IAT sensor if resistance is not as specified. If scan tool does not display DTC P0113 FAILED THIS IGN, go to «DIAGNOSTIC AIDS»(ref-12126-S39372549412000121100000).
4. Turn ignition off. Disconnect IAT sensor harness connector. Using a fused jumper wire, connect terminals of IAT sensor harness connector. Turn ignition on. Using scan tool, read IAT value. If reading is zero volts and 284°F (140°C), go to step 6. If reading is not as specified, go to next step.
5. Turn ignition off. Connect jumper between IAT sensor harness connector Yellow/Green wire and ground. Turn ignition on and observe IAT sensor value. If reading is zero volts and 284°F (140°C), go to step 7. If reading is not as specified, go to step 8.
6. Check for poor connections at IAT sensor and harness connector. Repair as necessary. If terminals and connector are okay, go to step 10.
7. Turn ignition off. Disconnect PCM harness connector. Check IAT sensor ground (Gray/Black wire) for an open circuit between IAT sensor harness connector and PCM harness connector terminal D9. see scheme 1and (Scheme 4). Repair as necessary. Retest system. If IAT ground circuit is okay, go to step 9.
8. Turn ignition off. Disconnect PCM harness connector. Check IAT sensor input (Yellow/Green wire) for an open circuit between PCM harness connector terminal B8 and IAT sensor harness connector. see scheme 1and (Scheme 4). Repair as necessary. Retest system. If IAT sensor input circuit is okay, go to next step.
9. Check PCM and IAT sensor harness connectors for poor connections or damaged terminals. Repair as necessary. Retest system. If terminals are okay, go to step 11.
10. Replace IAT sensor. Retest system.
11. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Engine Coolant Temperature (ECT) sensor is a thermistor that varies resistance based on temperature. As temperature of ECT sensor increases, resistance decreases. High temperature will result in a low signal voltage. ECT sensor value will be about 1.5-2.0 volts when engine is fully warmed.

Conditions required to set DTC are

1. Engine running for longer than two minutes.
2. ECT sensor signal indicates 302°F (150°C), about 0.14 volts for 12 seconds, over a 25-second period.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Move connectors and wiring harnesses related to ECT sensor. A change in scan tool display may indicate location of fault. If DTC cannot be duplicated, FAILURE RECORDS data can be used in determining vehicle mileage since DTC was last set. Check for ECT sensor out of range. See ECT SENSOR RESISTANCE VALUES table. If it is determined that DTC occurs intermittently, performing DTC P1114: ECT SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE may isolate cause of fault.

ECT SENSOR RESISTANCE VALUES

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. Using scan tool, read ENG COOL TEMP display. If temperature is less than 282°F (139°C), go to step 4. If temperature is 282°F (139°C) or greater, go to next step.
3. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, monitor specified DTC parameters. If scan tool displays DTC P0117 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0117 FAILED THIS IGN, see «DIAGNOSTIC AIDS»(ref-12126-S08336806782000121100000).
4. Disconnect ECT sensor harness connector. Using scan tool, read ENG COOL TEMP display. If reading is -38°F (-39°C) or less, go to step 6. If reading is more than specified, go to next step.
5. Turn ignition off. Disconnect PCM harness connectors. Check for faulty circuit in Blue/Red wire between ECT sensor harness connector and PCM harness connector terminal E9. see scheme 1and (Scheme 5). Repair as necessary. Retest system. If no problem was found, go to step 7.
6. Replace ECT sensor. Retest system.
7. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Scheme 5

Engine Coolant Temperature (ECT) sensor is a thermistor that varies resistance based on temperature. As temperature of ECT sensor increases, resistance decreases. High temperature will result in a low signal voltage. ECT sensor value will be about 1.5-2.0 volts when engine is fully warmed. DTC will set when PCM senses a continuous open in ECT sensor circuit.

Conditions required to set DTC are

1. Engine running time greater than 3 minutes.
2. ECT sensor signal indicates -38°F (-39°C) or less (about 5 volts) for 12 seconds over a 25-second period.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Move connectors and wiring harnesses related to ECT sensor. A change in scan tool display may indicate location of fault. If DTC cannot be duplicated, FAILURE RECORDS data can be used in determining vehicle mileage since DTC was last set. Check for ECT sensor out of range. See ECT SENSOR RESISTANCE VALUES table. If it is determined that DTC occurs intermittently, performing DTC P1115: ECT SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE may isolate cause of fault.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. Using scan tool, read ENG COOL TEMP display. If reading is less than -38°F (-39°C), go to step 4. If reading is -38°F (-39°C) or greater, go to next step.
3. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, monitor specified DTC parameters. If scan tool displays DTC P0118 FAILED THIS IGN, test ECT sensor. Using a DVOM, measure resistance across sensor terminals. See «ECT SENSOR RESISTANCE VALUES»(ref-12126-S19157083922000121100000) table. If scan tool does not display DTC P0118 FAILED THIS IGN, see «DIAGNOSTIC AIDS»(ref-12126-S22013087282000121100000).
4. Disconnect ECT sensor harness connector. Using fused jumper wire, connect ECT sensor harness connector terminals together. Using scan tool, read ENG COOL TEMP display. If temperature is 284°F (140°C) or greater, go to step 6. If temperature is not as specified, go to next step.
5. Connect jumper wire between ground and ECT sensor harness connector Blue/Red wire. Using scan tool, read ENG COOL TEMP display. If reading is 284°F (140°C) or greater, go to step 7. If reading is not as specified, go to step 8.
6. Check for faulty connection at ECT sensor. Repair as necessary and retest system. If connection is okay, go to step 10.
7. Turn ignition off. Disconnect PCM harness connectors. Check for open circuit in Blue wire between PCM harness connector terminal E8 and ECT sensor harness connector. see scheme 1and (Scheme 5). Repair as necessary. Retest system. If no problem was found, go to step 9.
8. Turn ignition off. Disconnect PCM harness connectors. Check for open circuit in Blue/Red wire between PCM harness connector terminal E9 and ECT sensor. see scheme 1and (Scheme 5). Repair as necessary and retest system. If no problem was found, go to next step.
9. Check for faulty ECT sensor input or ground circuit connection at PCM. Repair as necessary and retest system. If no problem is found, go to step 11.
10. Replace ECT sensor. Retest system.
11. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Throttle Position (TP) sensor measures amount of throttle plate opening. PCM uses TP sensor information for fuel delivery calculations. TP sensor reading is about 0.25 volts at closed throttle and 4.75 volts during Wide Open Throttle (WOT).

Conditions required to set DTC are

1. Engine running.
2. No MAP, ECT, TP, CKP, EGR, EVAP, injector or misfire DTCs set.
3. ECT reading is greater than 14°F (-10°C).
4. IAC counts are between 10 and 160 counts.
5. MAP value changes by less than 2 kPa.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. If connections and harness appear okay, observe TP and MAP displays on scan tool while moving all related harnesses and connectors. A change in scan tool display may indicate a fault. Check for MAP signal out of range or faulty MAP sensor by comparing scan tool values of a known-good similar vehicle. If DTC cannot be duplicated, FAILURE RECORDS data can be used in determining vehicle mileage since DTC was last set. If it is determined that DTC occurs intermittently, performing DTC P1121: TP SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE or DTC P1122: TP SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE may isolate cause of fault.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. With ignition on and engine off, review and record FAILURE RECORDS data on scan tool, then clear DTCs. Operate vehicle within FAILURE RECORDS conditions specified. Monitor specified DTC information. If scan tool indicates DTC P0121 RAN AND PASSED, go to «DIAGNOSTIC AIDS»(ref-12126-S05692780532000121100000). If scan tool does not indicate DTC P0121 RAN AND PASSED, go to next step.
3. Turn ignition on. While monitoring TP value on scan tool display, move throttle in a smooth even motion from closed position to WOT. If value displayed on scan tool changes smoothly from 0 percent (0.25 volt) to 100 percent (4.75 volts), go to next step. If TP value change is not smooth or does not change, go to step 11.
4. Turn ignition off. Disconnect TP sensor harness connector. Start vehicle and monitor TP value on scan tool. If TP value holds steady at 0-0.25 volt, go to step 6. If TP value does not remain at 0-0.25 volt, go to next step.
5. Turn ignition off. Disconnect all PCM harness connectors. Check for short to voltage in Blue wire (sensor input) between PCM harness connector terminal E8 and TP sensor harness connector. see scheme 1and (Scheme 6). Repair as necessary. Retest system. If no problem was found, go to step 12.
6. Check for open circuit or short to ground in Blue wire between PCM harness connector terminal E8 and TP sensor harness connector. see scheme 1and (Scheme 6). Repair as necessary and retest system. If no problem was found, go to step next step.
7. Check for faulty circuit on Red wire between TP sensor harness connector and PCM harness connector terminal A1. Repair as necessary. If no problem was found, go to next step.
8. Turn ignition off. Using a fused jumper wire, connect TP sensor harness connector Blue and Red wires together. While monitoring TP value on scan tool, turn ignition on. If TP value indicates about 5 volts and 100 percent, go to next step. If TP value is not as specified, go to step 12.
9. Turn ignition off. Disconnect all PCM harness connectors. Check for faulty TP sensor ground circuit between TP sensor and PCM harness connector terminal D8 (Green wire). see scheme 1and (Scheme 6). Repair as necessary and retest system. If no problem was found, go to next step.
10. Turn ignition off. Connect all PCM harness connectors. Using a DVOM, connect positive lead to TP sensor harness connector Red wire, and negative lead to TP sensor Green wire. Turn ignition on. If reading is about 5 volts, go to next step. If reading is not about 5 volts, go to step 12.
11. Replace TP sensor. Retest system.
12. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Scheme 6

Throttle Position (TP) sensor measures amount of throttle plate opening. PCM uses TP sensor information for fuel delivery calculations. TP sensor reading is about 0.25 volts at closed throttle and 4.75 volts during Wide Open Throttle (WOT).

Conditions required to set DTC are

1. Ignition switch in ON position.
2. TP sensor signal voltage is less than 0.235 volt for a period of .78 seconds over a 1.5 second period.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. If connections and harness appear okay, observe TP and MAP displays on scan tool while moving all related harnesses and connectors. A change in scan tool display may indicate a fault. If DTC cannot be duplicated, FAILURE RECORDS data can be used in determining vehicle mileage since DTC was last set. If it is determined that DTC occurs intermittently, performing DTC P1122: TP SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE may isolate cause of fault.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. With throttle closed, observe scan tool display. If TP sensor value reading is less than.235 volt, go to step 4. If TP sensor value is.235 volt or more, go to next step.
3. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions specified. Using scan tool, monitor specified DTC information. If scan tool indicates DTC P0122 RAN AND PASSED, go to «DIAGNOSTIC AIDS»(ref-12126-S11498468192000121100000). If scan tool does not indicate DTC P0122 RAN AND PASSED, go to next step.
4. Turn ignition off. Disconnect TP sensor. Using a fused jumper wire, connect TP sensor harness connector Red and Blue wires together. Turn ignition on. If TP sensor reading is about 5 volts, go to step 10. If reading is not as specified, go to next step.
5. Disconnect jumper wire. Connect a test light between positive battery terminal and TP sensor harness connector Blue wire. If TP sensor value reading on scan tool is about 5 volts, go to next step. If TP sensor value does not read about 5 volts, go to step 8.
6. Turn ignition off. Disconnect PCM harness connectors. Check for open or short circuit in Red wire between PCM harness connector terminal A1 and TP sensor harness connector. see scheme 1and (Scheme 6). Repair as necessary and retest system. If no problem was found, go to next step.
7. Inspect terminals of PCM, TP sensor and harness connectors for poor connection or damaged terminals. Repair as necessary. If terminals and connections are okay, go to step 12.
8. Turn ignition off. Disconnect PCM harness connectors. Check for faulty circuit in Blue wire between PCM harness connector terminal E8 and TP sensor harness connector. see scheme 1and (Scheme 6). Repair as necessary. Retest system. If no problem was found, go to next step.
9. Inspect terminals and harness connectors at PCM for poor connections or damaged terminals. Repair as necessary. If terminals and connections are okay, go to step 12.
10. Inspect terminals and harness connectors at TP sensor for poor connections or damaged terminals. Repair as necessary. If terminals and connections are okay, go to next step.
11. Replace TP sensor. Retest system.
12. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on, engine off. Using scan tool, read TP sensor value. If reading is more than 4.78 volts, go to step 4. If reading is 4.78 volts or less, go to next step.
3. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within conditions noted in FAILURE RECORDS data. Monitor specified DTC parameters data. If scan tool displays DTC P0123 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0123 FAILED THIS IGN, go to «DIAGNOSTIC AIDS»(ref-12126-S21368090872000121100000).
4. Turn ignition off. Disconnect TP sensor harness connector. Turn ignition on. Monitor TP SENSOR data. If reading is about zero volts, go to next step. If reading is not as specified, go to step 6.
5. Connect a test light between TP sensor harness connector Green wire and positive battery terminal. If test light does not illuminate, go to step 10. If test light illuminates, go to step 7.
6. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Check for short circuit to voltage in Blue wire between TP sensor harness connector and PCM harness connector terminal E8. see scheme 1and (Scheme 6). Repair as necessary and retest system. If no problem was found, go to step 12.
7. Turn ignition on. While monitoring scan tool TP SENSOR display, disconnect MAP sensor and FUEL PRESSURE (FP) sensor (one at a time). If display changes, replace component that causes change. Retest system. If display does not change, go to next step.
8. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Check for short to voltage in Red wire between PCM harness connector terminal A1 and TP sensor harness connector. see scheme 1and (Scheme 6) Repair as necessary and retest system. If no problem was found, go to next step.
9. Check for faulty connection at TP sensor. If faulty connection is found, repair as necessary and retest system. If connection is okay, go to step 11.
10. Turn ignition off. Disconnect PCM harness connectors. Check for open circuit in Green wire between PCM harness connector terminal D8 and TP sensor harness connector. see scheme 1and (Scheme 6). Repair as necessary and retest system. If circuit is okay, go to step 12.
11. Replace TP sensor. Retest system.
12. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

While engine is warming, PCM reads Engine Coolant Temperature (ECT) sensor to determine how long it takes coolant to reach temperature required for closed loop operation. PCM compares actual time required to a predetermined time.

Conditions required to set DTC are

Warm Case Test

1. No MAP, IAT, ECT, TP, Misfire, Injector or VSS DTCs set.
2. Start-up ECT less than 84°F (29°C).
3. Start-up IAT greater than 50°F (10°C).
4. Accumulated airflow is greater than 1500 grams.
5. Engine run time is more than 90 seconds.
6. Time for coolant to reach stabilized closed loop value is less than 120 seconds.

Cold Case Test

1. IAT is between 20°F (-7°C) and 50°F (10°C).
2. Accumulated airflow is greater than 2000 grams.
3. Engine run time is less than 225 seconds.
4. Time for coolant to reach stabilized closed loop value is less than 300 seconds.

Other Case Test

1. IAT is between -22°F (-30°C) and 20°F (-7°C).
2. Accumulated airflow is greater than 3600 grams.
3. Engine run time is less than 450 seconds.
4. Time for coolant to reach stabilized closed loop value is less than 600 seconds.

Check coolant level. Ensure thermostat and cooling fans are operating properly. Check for high resistance in wiring related to ECT sensor. Check for ECT sensor out of range by comparing actual coolant temperature with scan tool display, and replace ECT sensor if temperatures are not close. Check for faulty connections or damaged harness. If connections and harness appear okay, observe scan tool while moving all related harnesses and connectors. A change in scan tool display may indicate fault location. If DTC cannot be duplicated, FAILURE RECORDS data can be used in determining vehicle mileage since DTC was last set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. If any related ECT DTCs are set, diagnose affected DTC before proceeding. If no related ECT DTCs are set, go to next step.
3. Allow engine to cool. Check coolant level. If coolant level is low, go to step 9. If coolant level is okay, go to next step.
4. Start engine and allow it to idle. Using scan tool, monitor ENG COOL TEMP. If temperature increases to 70°F (21°C) within 2 minutes, see «DIAGNOSTIC AIDS»(ref-12126-S04400182332000121100000). If specified temperature is not reached within 2 minutes, go to next step. CAUTION: Use extreme caution when opening cooling system to measure coolant temperature.
5. Check thermostat operation. If thermostat is operating correctly, go to next step. If thermostat is not operating correctly, go to step 9.
6. Using thermometer, measure coolant temperature. Compare actual coolant temperature with scan tool ECT value. If temperatures are close in value, go to step 9. If temperatures are not close in value, go to next step.
7. Turn ignition off. Disconnect PCM harness connectors. Using a DVOM, measure ECT resistance between PCM harness connector terminals E8 (Green wire) and E9 (Blue/Red wire). see scheme 1 Compare DVOM readings with «ECT SENSOR RESISTANCE VALUES»(ref-12126-S19157083922000121100000) table. If measured resistance is as specified, go to step 12. If measured resistance is not as specified, go to next step.
8. Check for faulty circuits in Blue/Red and Green wires between ECT sensor and PCM harness connector. (Scheme 5) If a problem was found, go to step 10. If no problem was found, go to step 11.
9. Repair cooling system as necessary. Retest system.
10. Repair wiring or terminals as necessary. Retest system.
11. Replace ECT sensor. Retest system.
12. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

PCM reads Engine Coolant Temperature (ECT) sensor to determine if coolant reaches temperature required for closed loop operation. Conditions required to set DTC are

Cold Case

1. Engine starting temperature is more than 20°F (-7°C) and less than 50°F (10°C).
2. Accumulated airflow is more than 10,000 grams.
3. Accumulated idle time is less than 450 seconds.
4. Coolant temperature has not reached 165°F (74°C) after 800 seconds.

Warm Case

1. Accumulated idle time is less than 255 seconds.
2. Engine starting temperature is between 19°F (-7°C) and 99°F (37°C).

Check for poor connections at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connections. If connections and harness appear okay, observe ECT display on scan tool while moving all related harnesses and connectors. A change in scan tool display may indicate a fault location. If DTC cannot be duplicated, FAILURE RECORDS data can be used in determining vehicle mileage since DTC was last set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Inspect all cooling system hoses and pipes for kinks, proper connection and correct routing. Repair as necessary. If no problem was found, go to next step.
3. Remove thermostat. Suspend thermostat in water-filled container. Insert thermometer to monitor temperature. Observe thermostat operation while heating container. Thermostat should begin opening at 166-173°F (75-79°C). Thermostat should be fully open at 194°F (90°C). If thermostat operation is not as specified, replace thermostat. If thermostat operation is as specified, go to next step.
4. Turn ignition on. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within conditions noted in FAILURE RECORDS data. Monitor specified DTC parameters. If scan tool displays DTC P0128 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0128 FAILED THIS IGN, go to «DIAGNOSTIC AIDS»(ref-12126-S24115920002001080700000).
5. Using scan tool, observe ENG COOL TEMP display. If reading is less than 282°F (139°C), verify repairs and retest system. If reading is 282°F (139°C) or more, go to next step.
6. Turn ignition off. Disconnect PCM harness connectors. Check for faulty circuits in Blue/Red and Green wires between PCM harness connector and ECT sensor. see scheme 1and (Scheme 5). Repair as necessary and retest system. If no problem was found, go to «DIAGNOSTIC AIDS»(ref-12126-S24115920002001080700000).
7. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

PCM provides about .45 volt reference to Heated Oxygen Sensor (HO2S). HO2S sensor signal voltage varies from about one volt when exhaust is rich to about .1 volt when exhaust is lean. PCM reads and stores sensor voltage information during normal closed loop operation and evaluates voltage samples to determine amount of time sensor voltage is out of range. If HO2S-1 voltage is out of predetermined range for an extended period of time, DTC will set.

Conditions required to set DTC are

1. No related DTCs set.
2. Engine is running in closed loop.
3. Engine coolant temperature is greater than 140°F (60°C).
4. Closed loop commanded air/fuel ratio is between 14.5:1 and 14.8:1.
5. TP sensor angle is 5.9-50 percent.
6. HO2S-1 signal reading remains below 22 mV during normal closed loop operation for 77 seconds during a 90-second period.

Ensure HO2S-1 sensor harness is routed correctly and not contacting exhaust system. Check for faulty PCM grounds. Perform FUEL SYSTEM DIAGNOSIS under TROUBLE SHOOTING in BASIC DIAGNOSTIC PROCEDURES article.

Check for vacuum leaks at intake manifold, throttle body, EGR system and crankcase ventilation system. Check for exhaust leaks before HO2S-1. Check for fuel contamination.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Start engine and allow it to reach operating temperature. Operate vehicle under conditions required to set DTC. Using scan tool, read BANK 1 HO2S-1 voltage. If reading stays less than.3 volt, go to step 4. If reading is not as specified, go to next step.
3. Turn engine off, ignition on. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within FAILURE RECORDS parameters as noted on scan tool. Using scan tool, monitor specified DTC information. If scan tool displays DTC P0131 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0131 FAILED THIS IGN, see «DIAGNOSTIC AIDS»(ref-12126-S29742748802000121100000).
4. Turn ignition off. Disconnect PCM harness connectors. Check HO2S sensor harness connector White wire (high signal circuit) and Red wire (low signal circuit) for short to ground or to heater ground circuit. (Scheme 7) If short is found, go to next step. If no short is found, go to step 6.
5. Repair HO2S-1 signal circuit wiring as necessary. Retest system.
6. Turn ignition off. Check for continuity between White wire (high signal) and Red wire (low signal) circuits. If continuity exists, go to next step. If continuity does not exist, go to step 8.
7. Repair short circuit between White wire (high signal) and Red wire (low signal) circuits. Retest system.
8. Turn ignition off. Reconnect PCM harness connector, leaving HO2S disconnected. Turn ignition on. If scan tool reads 430-450 mV, see «DIAGNOSTIC AIDS»(ref-12126-S29742748802000121100000). If scan tool does not read 430-450 mV, go to next step.
9. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Scheme 7

PCM provides about .45 volt reference to Heated Oxygen Sensor (HO2S). HO2S sensor signal varies from about one volt when exhaust is rich to about .1 volt when exhaust is lean. PCM reads and stores sensor information during normal closed loop operation and evaluates samples to determine amount of time sensor reading is out of range. If HO2S-1 reading is out of predetermined range for an extended period of time, DTC will set.

Conditions required to set DTC are

1. No related DTCs set.
2. Engine coolant temperature is greater than 140°F (60°C).
3. Closed loop commanded air/fuel ratio is between 14.5:1 and 14.8:1.
4. TP sensor angle is 5.9-50 percent.
5. HO2S-1 signal remains greater than 952 mV during normal closed loop operation for 77 seconds during a 90-second period. Or
6. HO2S-1 signal stays greater than 500 mV during deceleration fuel cut-off mode operation for 5 seconds.

Check for excessive fuel pressure. Check injector balance. Check for leaking fuel pressure regulator. See FUEL SYSTEM DIAGNOSIS under TROUBLE SHOOTING in BASIC DIAGNOSTIC PROCEDURES article. Check HO2S-1 for silicon (powdery white deposit) contamination.

Check EVAP canister for fuel saturation. Disconnect MAF sensor connector and see if rich condition is corrected. If rich condition is corrected, check MAF sensor. Check for fuel in fuel pressure regulator vacuum line. Check TP sensor output for false information causing fuel system to go rich. Inspect for silicon contamination of HO2S, causing high HO2S-1 voltage signal.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Start engine and allow it to reach operating temperature. Operate vehicle under conditions required to set DTC. Using scan tool, read HO2S-1 value. If reading stays greater than 952 mV (500 mV in deceleration fuel cut-off mode), go to step 4. If reading stays lower than specified, go to next step.
3. Turn ignition on, engine off. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, monitor specified DTC parameters. If scan tool displays DTC P0132 RAN AND PASSED, go to «DIAGNOSTIC AIDS»(ref-12126-S39370351962000121100000). If scan tool does not display DTC P0132 RAN AND PASSED, go to next step.
4. Turn ignition off. Disconnect HO2S-1 harness connector. Turn ignition on. Using a DVOM, measure HO2S-1 value at HO2S-1 harness connector high signal (White wire) and low signal (Red wire) terminals. (Scheme 7) If readings are 5-14 volts, go to next step. If readings are not 5-14 volts, go to step 6.
5. Repair short to voltage in affected signal circuit between PCM harness connector and HO2S-1 harness connector. see scheme 1and (Scheme 7). Repair as necessary. Retest system.
6. Turn ignition off. Disconnect PCM harness connectors. Inspect PCM harness connector terminals C14 (Green wire) and C15 (White wire) for damage. see scheme 1 Repair as necessary. Retest system. If no problem was found, go to next step.
7. Turn ignition on. Disconnect HO2S and connect a jumper between HO2S high and low circuits to ground. Using a scan tool, read HO2S-1 value. If reading is less than 10 mV, go to next step. If reading is 10 mV or more, go to step 9.
8. Replace HO2S-1. Retest system.
9. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

PCM provides about .45 volt reference to Heated Oxygen Sensor (HO2S). HO2S sensor signal varies from about one volt when exhaust is rich to about .1 volt when exhaust is lean. PCM counts number or times a rich-to-lean and lean-to-rich response is indicated and adds amount of time it takes to complete all transitions. PCM uses this information to determine average time for each transition. If average response time is slow, DTC P0133 will set.

Conditions required to set DTC are

1. No related DTCs set.
2. Engine coolant temperature is greater than 140°F (60°C).
3. Engine operating in closed loop.
4. Engine speed is 1500-3500 RPM.
5. Canister purge solenoid duty cycle is greater than 2 percent.
6. Calculated airflow is 17-32 grams per second.

Check for faulty connections or damaged harness. Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. If connections and harness appear okay, observe HO2S-1 display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. If DTC cannot be duplicated, FAILURE RECORDS data can be used in determining vehicle mileage since DTC was last set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step. NOTE: Diagnose any DTCs set (except for DTCs P1133 or P1134), before proceeding.
2. Start engine and allow it to reach operating temperature. Operate vehicle within conditions required to set DTC. Using scan tool, monitor specified DTC parameters. If scan tool displays DTC P0133 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0133 FAILED THIS IGN, see «DIAGNOSTIC AIDS»(ref-12126-S07818801912000121100000).
3. If scan tool also displays DTC P1133 and/or P1134 FAILED THIS IGN, go to step 8. If scan tool does not display these DTCs, go to next step.
4. Visually inspect exhaust system for leaks near HO2S-1. If leaks are found, repair as necessary and return to step 2. If no leaks are found, go to next step.
5. Visually inspect HO2S-1 for secure installation, or corrosion on terminals. Check terminal tension at HO2S-1 and PCM. Check for damaged wiring. If any problems were found, go to step 9. If no problem was found, go to next step.
6. Disconnect HO2S-1 connector. Turn ignition on. Using a DVOM, measure voltage at HO2S harness connector between high signal circuit (White wire) and ground, and between low signal circuit (Red wire) and ground. If both readings are 3-4 volts, go to next step. If readings are not as specified, go to step 10.
7. Connect a jumper wire between HO2S-1 harness connector high signal (White wire) and low signal (Red wire) terminals and ground. Turn ignition on. Using scan tool, read HO2S-1 voltage. If reading is less than 10 mV and immediately returns to 450 mV when jumper wire is removed, go to step 12. If voltage is not as specified, go to step 13.
8. Replace affected HO2S. Retest system. NOTE: Before replacing HO2S, correct cause of HO2S contamination.
9. Repair condition as necessary. Retest system.
10. Inspect PCM harness connector terminals C14 (Green wire) and C15 (White wire) for damage. see scheme 1 Repair as necessary. Retest system. If PCM connections and terminals are in good condition, go to next step.
11. Repair open, short or grounded HO2S-1 signal circuit. Retest system.
12. Replace HO2S-1. Retest system.
13. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

PCM provides about .45 volt reference to Heated Oxygen Sensor (HO2S). HO2S sensor signal voltage varies from about one volt when exhaust is rich to about .1 volt when exhaust is lean. PCM constantly monitors HO2S signal during Closed Loop operation, and compensates for rich or lean condition by adjusting injector pulse width. If HO2S voltage remains at or near .45 volt reference voltage for an extended period of time, DTC will set.

Conditions required to set DTC are

1. No related DTCs set.
2. Engine has been running for at least 2 minutes.
3. HO2S heater has been determined to be functioning properly (HO2S has warmed to operating temperature).
4. HO2S signal voltage remains between .4-.5 volts for a specified period of time.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. If connections and harness appear okay, observe HO2S-1 display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. Check HO2S-1 heater operation. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine how often malfunction occurs.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Start engine and allow it to reach normal operating temperature. Apply parking brake and increase engine speed to greater than 1200 RPM for 3 minutes. Using scan tool, read HO2S-1 voltage. If reading stays around.4-.5 volts, go to step 4. If reading varies above and below.4-.5 volts, go to next step.
3. Turn engine off. Turn ignition on, engine off. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, monitor specified DTC parameters. If scan tool displays DTC P0134 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0134 FAILED THIS IGN, see «DIAGNOSTIC AIDS»(ref-12126-S12749169212000121100000).
4. Inspect HO2S-1 sensor wire harness for damage and repair as necessary. Retest system. If wire harness is okay, go to next step.
5. Check for faulty connection at HO2S-1 at high and low circuit terminals (Red and White wires). (Scheme 7) If faulty connection is found, repair as necessary. Retest system. If connection is okay, go to next step.
6. Inspect PCM harness connector terminals C14 (Green wire) and C15 (White wire) for damage. see scheme 1 Repair as necessary. Retest system. If connection is okay, go to next step.
7. Turn ignition off. Disconnect PCM harness connectors. Check resistance between HO2S-1 and PCM harness connector terminal C-14 (White wire). If resistance is greater than.5 ohm, repair open circuit or faulty connection as necessary. Retest system. If resistance is.5 ohms or less, go to next step.
8. Ensure ignition is off and PCM harness connectors are disconnected. Check resistance between HO2S and PCM harness connector terminal C-15 (Red wire at HO2S-1; changes to Green wire at PCM). If resistance is greater than.5 ohm, repair open circuit or faulty connection as necessary. Retest system. If resistance is.5 ohm or less, go to next step.
9. Turn ignition on, engine off. Disconnect HO2S harness connector. Connect jumper wires from HO2S-1 harness connector high (White wire) and low (Red wire) circuits to chassis ground. Using a scan tool, read voltage. If reading is about.10 volt, go to next step. If reading is not as specified, go to step 11.
10. Replace HO2S-1. Retest system.
11. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

PCM provides about .45 volt reference to Heated Oxygen Sensor (HO2S). HO2S sensor signal varies from about one volt when exhaust is rich to about .1 volt when exhaust is lean. When ignition is turned on, battery voltage is supplied to HO2S heater to provide for faster sensor warm-up, allowing sensor to become active in a shorter period of time. PCM reads amount of time necessary for sensor to become active after start-up. If too much time was required for HO2S to become active, DTC P0135 will set.

Conditions required to set DTC are

1. No related DTCs set.
2. Engine coolant and intake air temperatures are less than 90°F (32°C) at start-up.
3. Difference between ECT and IAT no greater than 44°F (7°C).
4. Ignition voltage is 11-16.6 volts.
5. MAF calculated airflow is less than 25 grams per second during sample period.
6. TP sensor angle is less than 40 percent.
7. HO2S-1 voltage does not change more than 148 mV from bias voltage (.4-.5 volts) for an extended period.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. If connections and harness appear okay, observe scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine how often malfunction occurs.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step. NOTE: If engine has been operating, allow engine to cool for about 30 minutes before proceeding with diagnostic testing.
2. Turn ignition on, engine off. Using scan tool, read HO2S-1 value. If readings are fluctuating and go from greater than.65 volt to less than.25 volt, see «DIAGNOSTIC AIDS»(ref-12126-S35925348262000121100000). If reading is not as specified, go to next step.
3. Inspect O2 SENSOR (20-amp) fuse in underhood fuse/relay block. If fuse is blown, go to step 15. If fuse is okay, go to next step.
4. Turn ignition off. Raise and support vehicle. Disconnect HO2S-1 harness connector. Connect a test light between chassis ground and HO2S-1 harness connector ignition feed (Red/Blue wire). (Scheme 7) If test light illuminates, go to next step. If test light does not illuminate, go to step 7.
5. Connect test light between HO2S-1 harness connector ignition feed (Red/Blue wire) and heater ground (Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 8.
6. Allow HO2S-1 to cool for at least 10 minutes. Using DVOM, check resistance between ignition feed (Red/Blue wire) and heater ground circuit (Black wire) at HO2S-1 connector (component side). (Scheme 7) If resistance is 3-6 ohms, go to step 9. If resistance is not as specified, go to step 10.
7. Repair open circuit in Red/Blue wire between O2 SENSOR (20-amp) fuse in underhood fuse/relay block and HO2S-1 harness connector. (Scheme 7) Retest system.
8. Repair open HO2S-1 heater ground circuit (Black wire). Retest system.
9. Check for faulty connection at HO2S-1 harness connector. If faulty connection is found, repair as necessary. Retest system. If connection is okay, go to next step.
10. Check for faulty connection at HO2S-1 harness connector Red/Blue and Black wires. If faulty connection is found, repair as necessary. Retest system. If connection is okay, go to next step.
11. Turn ignition off. Disconnect PCM harness connectors. Check resistance of Green wire (PCM side; changes to Red wire at HO2S-1 side) and White wire between PCM harness connector and HO2S-1 harness connector. see scheme 1and (Scheme 7). If resistance on either circuit is greater than 5 ohms, repair open or faulty connection as necessary. Retest system. If resistance is 5 ohms or less, go to next step.
12. Check Red wire for faulty connection at PCM harness connector terminal C15. see scheme 1 If faulty connection is found, repair as necessary. Retest system. If connection is okay, go to next step.
13. Check White wire for faulty connection at PCM harness connector terminal C14. If faulty connection is found, repair as necessary. Retest system. If connection is okay, go to next step.
14. Replace HO2S-1. Retest system.
15. Locate and repair shorted condition in HO2S-1 ignition feed circuit. (Scheme 7) Replace fuse. Retest system.

Three-Way Catalyst (TWC) system is used to control emissions. PCM uses signals from front Heated Oxygen Sensor (HO2S-1) to monitor pre-cat emissions, and compares those readings with HO2S-2 readings to monitor post-cat emissions. With both front and HO2S-2 sensor readings, PCM can evaluate efficiency of TWC. PCM will set DTC P0137 if TWC oxygen storage capacity, or HO2S-2 (HO2S-2) reading, is less than a predetermined threshold.

Conditions required to set DTC are

1. No related DTCs set.
2. Engine operating in closed loop.
3. Closed loop commanded air/fuel ratio is 14.5-14.8:1.
4. Engine coolant temperature is greater than 140°F (60°C).
5. TP sensor angle is 5.9-50 percent.
6. HO2S-2 signal stays less than .22 volts during closed loop operation for 106 seconds during a 125-second period. Or
7. HO2S-2 signal stays less than 426 millivolts during fuel enrichment mode for 5 seconds.

Ensure HO2S-2 sensor harness is routed correctly and not contacting exhaust system. Check for faulty PCM grounds. Check for low fuel pressure or lean fuel injectors. See FUEL SYSTEM DIAGNOSIS under TROUBLE SHOOTING in BASIC DIAGNOSTIC PROCEDURES article.

Check for vacuum leaks at intake manifold, throttle body, EGR system and crankcase ventilation system. Check for exhaust leaks upstream from HO2S-2. Check for fuel contamination. See FUEL SYSTEM DIAGNOSIS under TROUBLE SHOOTING in BASIC DIAGNOSTIC PROCEDURES article.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Start engine and allow it to reach operating temperature. Operate vehicle under conditions required to set DTC. Using scan tool, read BANK 1 HO2S-2 value. If reading remains less than.026 volt, go to step 4. If reading is not as specified, go to next step.
3. Turn engine off. Turn ignition on. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, monitor specified DTC parameters. If scan tool displays DTC P0137 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0137 FAILED THIS IGN, see «DIAGNOSTIC AIDS»(ref-12126-S36720108252000121100000).
4. Turn ignition off. Disconnect PCM harness connectors. Check HO2S-2 sensor harness connector high and low signal circuits for short circuit to ground or to HO2S heater ground. see scheme 1and (Scheme 7). If short is found, go to next step. If no short is found, go to step 6.
5. Repair HO2S-2 circuit as necessary. Retest system.
6. With ignition off, leaving PCM and HO2S-2 harness connectors disconnected, check for continuity between high and low signal circuits. (Scheme 7) If continuity exists, go to next step. If continuity does not exist, go to step 8.
7. Repair short circuit between high and low signal circuits. Retest system.
8. With ignition off, reconnect PCM, leaving HO2S disconnected. Turn ignition on. Using scan tool, read HO2S-2 value. If reading is.43-.45 volt, go to «DIAGNOSTIC AIDS»(ref-12126-S36720108252000121100000). If reading is not as specified, go to next step.
9. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Three-Way Catalyst (TWC) system is used to control emissions. PCM uses signals from front Heated Oxygen Sensor (HO2S-1) to monitor pre-cat emissions, and compares those readings with HO2S-2 readings to monitor post-cat emissions. With both front and HO2S-2 sensor readings, PCM can evaluate efficiency of TWC. PCM will set DTC P0138 if HO2S-2 readings remain excessively high for an extended period of time.

Conditions required to set DTC are

1. No related DTCs set.
2. Engine operating in closed loop.
3. Closed loop commanded air/fuel ratio is 14.5-14.8:1.
4. Engine coolant temperature is greater than 140°F (60°C).
5. TP sensor angle is 5.9-50 percent. All of above conditions met for 3.0 seconds or in "Deceleration Fuel Cutoff" mode, and one of following two conditions are met
6. HO2S-2 signal stays greater than .952 of a volt during closed loop operation for a specified period of time.
7. HO2S-2 signal stays greater than .474 of a volt during deceleration fuel cutoff mode.

Ensure HO2S-2 sensor harness is routed correctly and not contacting exhaust system. Check for excessive fuel pressure or rich injector. Check for leaking fuel pressure regulator. Check for fuel in fuel pressure regulator vacuum hose. See FUEL SYSTEM DIAGNOSIS under appropriate TROUBLE SHOOTING in BASIC DIAGNOSTIC PROCEDURES article. Check for internally shorted HO2S-2. Check HO2S-2 for silicon (powdery, White deposit) contamination. Check for intermittent TP sensor output malfunction. Check for faulty PCM grounds. Check for open or short in HO2S-2 signal or ground circuits. Check EVAP canister for fuel saturation.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Start engine and allow it to reach operating temperature. Operate vehicle under conditions required to set DTC. Using scan tool, read HO2S-2 value. If reading remains greater than.952 volt, go to step 4. If reading is not as specified, go to next step.
3. Turn ignition on. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, monitor specified DTC parameters. If scan tool displays DTC P0138 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0138 FAILED THIS IGN, see «DIAGNOSTIC AIDS»(ref-12126-S41193145002000121100000).
4. Turn ignition off. Disconnect HO2S-2 connector. Turn ignition on. Using a DVOM, measure voltages at high and low signal terminals of HO2S-2 harness connector (PCM side). (Scheme 7) If readings are between 5-14 volts, go to next step. If readings are not as specified, go to step 6.
5. Repair short to voltage in HO2S-2 signal circuit. (Scheme 7) Retest system.
6. Turn ignition off. Disconnect PCM harness connectors. Inspect PCM harness connector terminals C16 (Orange/Blue wire) and D16 (White/Blue wire) for damage. see scheme 1 Repair as necessary and retest system. If no problem is found, go to next step.
7. Turn ignition on. Using jumper wires, connect HO2S-2 sensor high and low signal terminals to chassis ground. (Scheme 7) Using scan tool, read HO2S-2 value. If reading is less than.01 volt, go to next step. If reading is greater than.01 volt, go to step 9.
8. Replace HO2S-2. Retest system.
9. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Three-Way Catalyst (TWC) system is used to control emissions. PCM uses signal from rear Heated Oxygen Sensor (HO2S-2) located behind TWC, to determine efficiency of TWC. PCM will set DTC P0140 if HO2S signal voltage remains between .4-.5 volts for an extended period of time.

Conditions required to set DTC are

1. No related DTCs set.
2. Engine running time is longer than 2 minutes.
3. HO2S-2 heater is operating properly, and HO2S-2 is at operating temperature.
4. Engine is operating in closed loop.
5. HO2S-2 signal remains between 426-474 millivolts for 106 seconds during a 125-second period.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. If connections and harness appear okay, observe HO2S display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. Check HO2S-2 heater operation.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Start engine and allow it to reach operating temperature. Increase engine speed to greater than 1200 RPM for 2 minutes. Using scan tool, read HO2S-2 value. If reading is switching outside of.425-.475 volt range, go to next step. If reading stays within.425-.475 volts, go to step 4.
3. Turn engine off. Turn ignition on, engine off. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, monitor specified DTC parameters. If scan tool displays DTC P0140 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0140 FAILED THIS IGN, see «DIAGNOSTIC AIDS»(ref-12126-S16011989522000121100000).
4. Check for faulty connection at HO2S-2 harness connector. If faulty connection is found, repair as necessary. Retest system. If connection is okay, go to next step.
5. Turn ignition off. Check for faulty connection at PCM harness connector terminals C16 (Orange/Blue wire) and D16 (White/Blue wire). see scheme 1 If faulty connection is found, repair as necessary. Retest system. If connection is okay, go to next step.
6. Turn ignition off. Disconnect PCM harness connectors. Check resistance of HO2S-2 harness connector high and low signal circuits. see scheme 1and (Scheme 7). If resistance is greater than 5 ohms, repair open or faulty connection as necessary. Retest system. If resistance is 5 ohms or less, go to next step.
7. Reconnect PCM harness. Turn ignition on. Using DVOM, check voltage between each HO2S-2 harness connector terminal signal circuit and heater ground circuit. (Scheme 7) If reading is about 3-4 volts, go to step 9. If reading is not as specified, go to next step.
8. Check both signal circuits for a short to ground or voltage. Repair as necessary. Retest system. If no problem was found, go to step 11.
9. Disconnect HO2S-2 harness connector. Connect jumper wires between HO2S-2 harness connector high and low signal circuits and heater ground terminal. Using scan tool, read HO2S-2 voltage. If reading is 0-.01 volt, go to next step. If reading not 0-.01 volt, go to step 11.
10. Replace HO2S-2. Retest system.
11. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

When ignition is turned on, battery voltage is supplied to HO2S heater to provide for faster sensor warm-up, allowing sensor to become active in a shorter period of time. PCM reads amount of time necessary for sensor to become active after start-up.

Conditions required to set DTC are

1. No related DTCs set.
2. Engine coolant and intake air temperatures are less than 90°F (32°C) at start-up.
3. Difference between ECT and IAT no greater than 44°F (6.75°C).
4. Ignition voltage is 11-16.6 volts.
5. Throttle angle is less than 40 percent.
6. MAF calculated airflow is less than 26 grams per second.
7. HO2S-2 reading remains within .15 volt of bias reading (.4-.5 volt) for longer amount of time than it should.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. If connections and harness appear okay, observe scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step. NOTE: If engine has been operating, allow engine to cool for about 30 minutes before proceeding with diagnostic tests.
2. Turn ignition on. Using scan tool, read HO2S-2 value. If reading varies between greater than.65 volts and less than.25 volts, see «DIAGNOSTIC AIDS»(ref-12126-S42558697492000121100000). If reading is not as specified, go to next step.
3. Inspect HO2S SENSOR (20-amp) fuse. If fuse is open, go to step 15. If fuse is okay, go to next step.
4. Turn ignition off. Raise and support vehicle. Disconnect HO2S-2 harness connector. Connect a test light to chassis ground, and probe HO2S-2 ignition feed circuit (Red/Blue wire). (Scheme 7) If test light illuminates, go to next step. If test light does not illuminate, go to step 7.
5. Connect test light between HO2S-2 harness connector ignition feed (Red/Blue wire) and heater ground (Black wire) circuits. If test light illuminates, go to next step. If test light does not illuminate, go to step 8.
6. Allow HO2S-2 to cool for at least 10 minutes. Using DVOM, check resistance between ignition feed and heater ground circuits at HO2S-2 harness connector (sensor side). (Scheme 7) If resistance is 3-6 ohms, go to step 9. If resistance is not as specified, go to step 10.
7. Repair open HO2S-2 ignition feed circuit. Retest system.
8. Repair open HO2S-2 heater ground circuit. Retest system.
9. Check for faulty connection at HO2S-2. If faulty connection is found, repair as necessary. Retest system. If connection is okay, go to next step.
10. Turn ignition off. Disconnect PCM harness connectors. Check resistance of HO2S-2 signal high and low circuits. see scheme 1and (Scheme 7). If resistance on either circuit is greater than 5 ohms, repair open circuit or faulty connection. Retest system. If resistance is 5 ohms or less, go to next step.
11. Check for faulty connection at HO2S-2 harness connector. If faulty connection is found, repair as necessary. Retest system. If connection is okay, go to next step.
12. Check for faulty HO2S-2 low signal circuit connection at PCM harness connector terminal D16 (White/Blue wire). If faulty connection is found, repair as necessary. If connection is okay, go to next step.
13. Check for faulty HO2S-2 high signal circuit connection at PCM harness connector terminal C16 (Orange/Blue wire). If faulty connection is found, repair as necessary. Retest system. If connection is okay, go to next step.
14. Replace HO2S-2. Retest system.
15. Locate and repair shorted condition in HO2S-2 ignition feed circuit and replace fuse. (Scheme 7) Retest system.

PCM reads HO2S signal voltage and adjusts fuel delivery based on this voltage. A change made to fuel delivery is indicated by Long Term (LT) and Short Term (ST) FUEL TRIM values.

ST FUEL TRIM values change rapidly in response to HO2S signal voltages. These changes fine tune engine fuel delivery. LT FUEL TRIM values change in response to trends in ST fuel trim. LT fuel trim makes coarse adjustments to fueling in order to re-center and restore control to ST fuel trim.

Ideal FUEL TRIM value is about zero. Fuel trim value more than zero indicates PCM is adding fuel to compensate for a lean condition. Fuel trim less than zero indicates PCM is reducing amount of fuel to compensate for rich condition. DTC will set if PCM detects an excessively lean condition.

Conditions required to set DTC are

1. No scan tool test is being run.
2. No emission related DTCs set.
3. Engine coolant temperature is 149-219°F (65-104°C).
4. Intake air temperature is -40-248°F (-40-120°C).
5. MAP sensor values are between 23.75-99 kPa.
6. Barometric pressure is more than 72.3 kPa.
7. Engine speed is 400-6000 RPM.
8. System voltage is greater than 9.5 volts.
9. Engine is operating in closed loop.
10. Average short term fuel trim is greater than 1.012.
11. Adaptive index multiplier samples are greater than 1.266.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. If connections and harness appear okay, observe scan tool HO2S-1 display while moving all related harnesses and connectors. A change in scan tool display indicates fault location. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. If any DTC other than P0171 is set, diagnose affected DTC before proceeding. If no other DTC is set, go to next step.
3. Operate vehicle in closed loop. Using scan tool, read BANK 1 LT FUEL TRIM values. If LT FUEL TRIM value is greater than 20 percent, go to step 5 . If value is not as specified, go to next step.
4. Using scan tool, read and record FAILURE RECORDS data. Clear DTCs and operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, monitor specified DTC parameters while operating vehicle. Continue operating vehicle until DTC P0171 test runs. If scan tool displays DTC P0171 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0171 FAILED THIS IGN, condition is not present. Go to TROUBLE SHOOTING - NO CODES article.
5. Check vacuum hoses for splits, kinks and proper routing. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
6. Check PCV valve for proper operation and installation. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
7. Start engine. If high or unsteady idle condition exists, go to next step. If idle is okay, go to step 10 .
8. Using scan tool, read IDLE AIR CONTROL value. If value is more than 5 counts, go to step 10 . If value is 5 counts or less, go to next step.
9. Check throttle body, intake manifold, and EGR valve for vacuum leaks. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
10. Check IAC valve for proper operation. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
11. Check for fuel contamination. If fuel is contaminated, repair condition causing contamination. Retest system. If fuel is okay, go to next step.
12. Check PCM injector, power and sensor grounds for clean and tight connections, and for proper location. See WIRING DIAGRAMS article. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
13. Perform fuel system pressure test. See FUEL PUMP PRESSURE TEST under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
14. Ensure evaporative emission system is functional. See «DTC P0443: EVAP SYSTEM PURGE CONTROL VALVE CIRCUIT MALFUNCTION»(ref-12126-S36797006692000121100000) . If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
15. Check intake manifold, injector "O" rings, EGR adapter, EGR valve, and EGR feed pipes for vacuum leaks. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
16. Check exhaust system for leaks, loose or missing hardware. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
17. Check fuel injector operation. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEM in SYSTEM & COMPONENT TESTING article. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
18. Ensure HO2S is installed securely, and connector and harness are not contacting exhaust manifold. If a problem is found, repair as necessary. Retest system. If no problem is found, go to «DIAGNOSTIC AIDS»(ref-12126-S10000032902000121100000) .

PCM reads HO2S signal voltage and adjusts fuel delivery accordingly. A change made to fuel delivery is indicated by Long Term (LT) and Short Term (ST) FUEL TRIM values.

ST FUEL TRIM values change rapidly in response to HO2S signal voltages. These changes fine tune engine fuel delivery. LT FUEL TRIM values change in response to trends in ST fuel trim. LT fuel trim makes coarse adjustments to fueling in order to re-center and restore control to ST fuel trim. LT and ST fuel trim can be read by using a scan tool.

Ideal FUEL TRIM value is about zero percent. Fuel trim value more than zero percent indicates that PCM is adding fuel to compensate for a lean condition. Fuel trim less than zero percent indicates that PCM is reducing amount of fuel to compensate for rich condition. DTC will set if PCM detects an excessively rich condition.

Conditions required to set DTC are

1. No scan tool test is being run.
2. Engine running more than 500 seconds.
3. No emission related DTCs set.
4. Engine coolant temperature is between 149-219°F (65-104°C).
5. Intake air temperature is between -40 and 248°F (-40 and 120°C).
6. MAP is 23.75-99 kPa.
7. System voltage is greater than 9.5 volts.
8. Engine speed is 400-6000 RPM.
9. Barometric pressure is greater than 72.3 kPa.
10. Engine is operating in closed loop.
11. Average long term fuel trim is less than .988.
12. Adaptive index multiplier samples is 0.914 or less.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. If connections and harness appear okay, observe scan tool HO2S-1 display while moving all related harnesses and connectors. A change in scan tool display indicates fault location. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. If any DTCs other than P0172 are set, diagnose other DTCs before proceeding. If no other DTCs are set, go to next step.
3. Operate vehicle in closed loop mode while using scan tool to read BANK 1 LT FUEL TRIM values. If BANK 1 LT FUEL TRIM value is more negative than -14 percent, go to step 5 . If value is not as specified, go to next step.
4. Using scan tool, read and record FAILURE RECORDS data. Clear DTCs and operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, monitor specified DTC parameters while operating vehicle. Continue operating vehicle until DTC P0172 test runs. If scan tool displays DTC P0172 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0172 FAILED THIS IGN, condition is not present. Go to SYMPTOMS in TROUBLE SHOOTING - NO CODES article.
5. Check air filter element condition. Replace air filter element if necessary. Retest system. If air filter element is okay, go to next step.
6. Check for collapsed or restricted air intake duct. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
7. Start engine. If low or unsteady idle condition exists, go to next step. If idle is okay, go to step 10 .
8. Using scan tool, read IDLE AIR CONTROL value. If value is less than 100 counts, go to step 10 . If value is 100 counts or more, go to next step.
9. Turn ignition off. Check throttle body bore, throttle plate and IAC passages for coking and foreign objects. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
10. Check IAC valve for proper operation. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
11. Disconnect vacuum hose from fuel pressure regulator and check it for presence of fuel. If fuel is present, replace fuel pressure regulator. Retest system. If no fuel is present, go to next step.
12. Turn ignition on, engine off. Using scan tool, read TP ANGLE while slowly depressing accelerator pedal. If TP ANGLE increases steadily from 0 percent at closed throttle to 100 percent at wide open throttle, go to next step. If TP ANGLE does not increase as specified, go to step 17 .
13. Perform fuel system pressure test. See FUEL PUMP PRESSURE TEST under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
14. Ensure evaporative emission system is functional. See «DTC P0443: EVAP SYSTEM PURGE CONTROL VALVE CIRCUIT MALFUNCTION»(ref-12126-S36797006692000121100000) . If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
15. Perform FUEL INJECTOR BALANCE TEST under FUEL SYSTEM in SYSTEM & COMPONENT TESTING article. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
16. Remove HO2S-1 and check it for silicone (powdery White deposit) contamination. If HO2S-1 is contaminated, replace HO2S-1. Retest system. If HO2S-1 is not contaminated, go to «DIAGNOSTIC AIDS»(ref-12126-S37253981072000121100000) .
17. Check and tighten TP sensor mounting screws. If mounting screws are tight, replace TP sensor. Retest system.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Attempt to start engine. If engine starts, go to next step. If engine does not start, see ENGINE CRANKS BUT WILL NOT RUN under NO START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES article.
3. Using scan tool, clear DTCs. Run engine at idle for one minute and check scan tool. If DTC P0201-P0204 has reset, go to step 5. If DTC P0201-P0204 has not set, go to next step.
4. Turn engine off. Turn ignition on. Using scan tool, read FREEZE FRAME data and note parameters. Operate vehicle within FREEZE FRAME conditions. If DTC P0201-P0204 resets, go to next step. If no DTC is set, go to «DIAGNOSTIC AIDS»(ref-12126-S34874444602000121100000). NOTE: Gray 5-pin fuel injector test connector is located at right rear of valve cover. It can be identified by Blue connector lock.
5. Turn ignition off. Disconnect fuel injector test connector. (Scheme 8) Connect Injector Test Light (J39021-45) to injector test connector. Crank engine. If Injector Test Light for pertinent cylinder flashes, perform fuel injector coil test. See FUEL INJECTION under FUEL SYSTEM in SYSTEM & COMPONENT TESTING article. If Injector Test Light does not flash, go to next step.
6. If Injector Test Light for pertinent cylinder was on steadily in previous step, go to next step. If Injector Test Light was not on steadily in previous step, go to step 10.
7. Disconnect PCM harness connector for affected injectors. Using test light connected to battery positive terminal, probe affected injector driver circuit at PCM harness connector. see scheme 1and (Scheme 9). If test light illuminates, go to next step. If test light does not illuminate, go to step 9.
8. Repair short to ground in affected injector driver circuit. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000).
9. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000).
10. Disconnect injector test connector. Turn ignition on. Connect test light to chassis ground and probe each terminal of injector harness connector (PCM side). (Scheme 9) If test light illuminates on IGN (+) terminal (Red/Blue wire) only, go to step 12. If test light illuminates on other terminals besides IGN (+) terminal, go to next step.
11. Repair short to voltage in affected injector driver circuit. Retest system.
12. With test light still connected to ground, probe injector driver circuit (harness side). If test light illuminates on any terminal, go to step 11. If test light does not illuminate, go to next step.
13. Turn ignition off. Using an ohmmeter, check for an open between ignition terminal of injector test connector (Red/Blue wire) and each of the other terminals of injector test connector. (Scheme 9) If all terminals have continuity, go to step 15. If any terminals were open, go to next step.
14. Repair open in injector drive circuit or injector. Retest system.
15. Check for an open in pertinent injector control circuit between injector test connector and PCM harness connector. see scheme 1and (Scheme 9). If circuit is open, repair as necessary. Retest system. If circuit is okay, replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Scheme 8

Scheme 9

If PCM determines that engine is misfiring, but can not determine which cylinder is causing misfire, DTC P0300 will be set. This normally occurs when an ignition coil malfunctions because it fires more than one cylinder.

Conditions required to set DTC are

1. No related DTCs set.
2. Engine speed is 687-6250 RPM.
3. System voltage is 11-16 volts.
4. ECT value is between 20°F-248°F (7°C-120°C).
5. Throttle angle is steady and changes less than 2.73 percent per 100 milliseconds.
6. PCM detects crankshaft RPM variation, indicating a misfire which could cause catalytic convertor damage or high emissions.
7. TP sensor reads less than 3.125 percent.
8. Vehicle speed is greater than 12 MPH.
9. Fuel level is greater than 14.8 percent.

Using scan tool, read MISFIRE CUR # display for each cylinder. This will help locate and isolate which cylinder is affected by misfiring. Check secondary ignition wires. Check for damaged or faulty ignition coils. Substitute a known-good ignition coil. Check system grounds. Check air induction system, fuel pressure, injectors, and EGR valve. Excessive engine vibration could cause DTC to set. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine how often condition occurs.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Start engine and allow it to idle. Using scan tool, read and record FREEZE FRAME data. Operate vehicle within conditions noted in FREEZE FRAME data. Using scan tool, read MISFIRE CUR # display for each cylinder. If MISFIRE CUR # is increasing (indicating a misfire currently occurring) for any cylinder, go to next step. If MISFIRE CUR # is not increasing, go to «DIAGNOSTIC AIDS»(ref-12126-S16884606932000121100000).
3. Check vacuum hoses for splits, kinks, or improper connections. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
4. Check intake manifold, injector "O" rings, EGR valve, and EGR feed pipes for vacuum leaks. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
5. Check PCV valve for improper installation or damaged hose. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
6. Remove ignition coils. Check ignition coils for cracks or carbon tracking. If a problem is found, replace damaged ignition coils. Retest system. If no problem is found, go to next step.
7. Remove EGR valve and inspect valve, seat and passages for damage. Inspect valve pintle to ensure it is not sticking partially open. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
8. Install a spark tester on spark plug wire at spark plug end for cylinder indicating most severe misfire. Crank engine and check for crisp, Blue spark at tester. Repeat procedure for each affected cylinder. If spark is okay on all cylinders, go to step 12. If spark is not okay on any cylinder, go to next step.
9. Remove spark plug(s) associated with misfiring cylinder(s). Check spark plugs for excessive fouling. If spark plugs are excessively fouled, diagnose and repair mechanical engine problem. If spark plugs are not excessively fouled, go to next step.
10. Check spark plug insulation for cracks, carbon tracking or other damage. If a problem is found, replace faulty spark plug(s). Retest system. If no problem is found, go to next step.
11. Replace ignition control module. Retest system.
12. Check PCM injector, power and sensor grounds for clean and tight connection, and for proper location. See WIRING DIAGRAMS article. (Scheme 10) If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
13. Perform a fuel pump pressure test. See FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If a problem was found, repair as necessary. Retest system. If no problem was found, go to next step.
14. Check for fuel contamination. If fuel is contaminated, repair condition causing contamination. Retest system. If fuel is okay, go to next step.
15. Perform FUEL INJECTOR BALANCE TEST under FUEL SYSTEM in SYSTEM & COMPONENT TESTING article. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
16. Diagnose mechanical engine problems such as faulty or incorrect camshaft, leaking valves or piston rings, sticky valves, excessive valve deposits, loose or worn rocker arms, weak valve springs, incorrect valve timing, leaking head gasket, or loose or broken motor mounts. If a problem is found, repair as necessary. Retest system.

Scheme 10

If PCM determines engine is misfiring and can determine actual cylinder that is misfiring, DTC P0301-P0304 will set. This is normally caused by failed fuel injector, spark plug or spark plug wire.

Conditions required to set DTC are

1. No related DTCs set.
2. Engine speed is 687-6250 RPM.
3. System voltage is 11-16 volts.
4. ECT value is between 20-248°F (-7-120°C).
5. Throttle angle is steady and changes less than 2.73 percent per 100 milliseconds.
6. PCM detects crankshaft RPM variation, indicating a misfire which could cause catalytic convertor damage or high emissions.
7. TP sensor reads less than 3.125 percent.
8. Vehicle speed is greater than 12 MPH.
9. Engine under a load.
10. Fuel level is more than 14.8 percent.

Using scan tool, read MISFIRE CUR # display for each cylinder. This will help locate and isolate which cylinder misfire is affecting. Check secondary ignition wires. Check for damaged or faulty ignition coil. Substitute a known-good ignition coil. Check system grounds. Check air induction system, fuel pressure, injectors, and EGR valve. Excessive engine vibration could cause DTC to set. FAILURE RECORDS data can be used in determining vehicle mileage since DTC was last set and may help to learn how often condition occurs.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Start engine and allow it to idle. Using scan tool, read and record FREEZE FRAME data. Operate vehicle within conditions noted in FREEZE FRAME data. Using scan tool, read MISFIRE CUR # display for each cylinder. If MISFIRE CUR # is increasing (indicating a misfire currently occurring) for any cylinder, go to next step. If MISFIRE CUR # is not increasing, go to «DIAGNOSTIC AIDS»(ref-12126-S16884606932000121100000).
3. Check vacuum hoses for splits, kinks, or improper connections. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
4. Check intake manifold, injector "O" rings, EGR valve, and EGR feed pipes for vacuum leaks. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
5. Check PCV valve for improper installation or damaged hose. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
6. Remove ignition coils. Check ignition coils for cracks or carbon tracking. If a problem is found, replace damaged ignition coils. Retest system. If no problem is found, go to next step.
7. Install a spark tester on spark plug wire at spark plug end for cylinder indicated by DTC. Crank engine and check for crisp, Blue spark at tester. If spark is okay, go to step 12. If spark is not okay, go to next step.
8. Remove spark plug(s) associated with misfiring cylinder(s). Check spark plugs for excessive fouling. If spark plugs are excessively fouled, diagnose and repair mechanical engine problem. If spark plugs are not excessively fouled, go to next step.
9. Check spark plug insulation for cracks, carbon tracking or other damage. If a problem is found, replace faulty spark plug(s). Retest system. If no problem is found, go to next step.
10. Replace ignition control module. Retest system.
11. Check PCM injector, power and sensor grounds for clean and tight connection, and for proper location. See WIRING DIAGRAMS article. (Scheme 10) If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
12. Perform a fuel pump pressure test. See FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If a problem was found, repair as necessary. Retest system. If no problem was found, go to next step.
13. Check for fuel contamination. If fuel is contaminated, repair condition causing contamination. Retest system. If fuel is okay, go to next step.
14. Perform FUEL INJECTOR BALANCE TEST under FUEL SYSTEM in SYSTEM & COMPONENT TESTING article. If a problem was found, repair as necessary. Retest system. If no problem was found, go to next step.
15. Diagnose mechanical engine problems such as faulty or incorrect camshaft, leaking valves or piston rings, sticky valves, excessive valve deposits, loose or worn rocker arms, weak valve springs, incorrect valve timing, leaking head gasket, or loose or broken motor mounts. If a problem is found, repair as necessary. Retest system.

Knock sensor is used to detect engine detonation. Knock sensor produces and sends an AC voltage signal to PCM to identify engine knock being detected. PCM will retard timing based on this signal.

Conditions required to set DTC are

1. Engine running time greater than 10 seconds.
2. DTC P0327 is not set.
3. Engine speed is above 2500 RPM.

Check for faulty connections or damaged harness. Correct any abnormal engine noises. Any audible noise that causes a knocking type noise on engine block may be misinterpreted by knock sensor. Check for an open ignition feed.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Start engine. Using scan tool, clear DTCs. Run engine at slightly more than 10 percent throttle angle. If MIL illuminates, go to step 4. If MIL does not illuminate, go to next step.
3. Turn engine off. Turn ignition on. Review FREEZE FRAME data and note readings. Operate vehicle within conditions noted for setting DTC. If MIL illuminates, go to next step. If MIL does not illuminate, go to step 13.
4. Listen to engine while increasing and decreasing engine speed. If an abnormal audible noise is present, go to next step. If an abnormal audible engine noise is not present, go to step 6.
5. Repair cause of abnormal engine noise. Go to step 13.
6. While observing scan tool, slowly increase engine speed to 2500 RPM. If KS count increases with engine RPM, go to next step. If KS count does not increase with engine RPM, go to step 9.
7. Turn ignition off. Inspect PCM and KS harness connectors and terminals for damage. If connections are okay, go to next step. If either connection needed repair, go to step 13.
8. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Go to step 13.
9. Turn ignition off. Disconnect PCM harness connectors. Using a DVOM connected to ground, measure resistance of KS at PCM harness connector terminal A2. see scheme 1and (Scheme 11). If reading is 90-110 k/ohms, go back to step 7. If reading is not as specified, go to next step.
10. Check knock sensor harness connector for a poor connection and repair as necessary. If connector is okay, go to next step. If repair was necessary, go to step 13.
11. Check KS signal circuit for an open or shorted condition. (Scheme 11) Repair as necessary and go to step 13. If an open or shorted condition does not exist in KS circuit, go to next step.
12. Replace knock sensor. Go to next step.
13. Using scan tool, clear DTCs. Start engine and idle at normal operating temperature. Operate vehicle within conditions for setting DTC. If scan tool indicates this diagnostic has RAN AND PASSED, go to next step. If scan tool does not indicate this diagnostic has RAN AND PASSED, go back to step 2.
14. Check for any additional DTCs. If additional DTCs are set, see appropriate DIAGNOSTIC TEST for DTC set. If no other DTCs exist, system is okay.

Scheme 11

Knock sensor is used to detect engine detonation. Knock sensor produces and sends an AC voltage signal to PCM to identify that engine knock is being detected. PCM will retard timing based on this signal. PCM may reject a signal that appears to be a false signal. If PCM still detects a high noise level, DTC P0327 will be set.

Conditions required to set DTC are

A/D Test

1. Engine speed is 2500 RPM or greater.
2. A/D voltage is .0781 volts or less.
3. Engine coolant temperature is more than 140°F (60°C).
4. Engine vacuum is less than 35 kPa.
5. Abnormal noise level sensed for 8 seconds of 10-second period.

Gain Test

1. Engine speed is greater than 2500 RPM.
2. Gain is 23.875 decibels or more.

Check for faulty connections or damaged harness, backed out terminals or misrouted wiring harnesses. Correct any abnormal engine noises. Any audible noise that causes a knocking type noise on engine block may be misinterpreted by knock sensor. Scan tool will display knock sensor value in counts, increasing with engine speed and decreasing when engine speed decreases. Check internal resistance of knock sensor to verify component or wiring problem in knock sensor circuit.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Start engine. Using scan tool, operate vehicle within conditions specified to set DTC. Monitor specified DTC information until P0327 test runs. Observe and record test results. If scan tool indicates DTC P0327 FAILED THIS IGNITION, go to step 4. If scan tool does not indicate DTC P0327 FAILED THIS IGNITION, go to next step.
3. Turn engine off. Turn ignition on. Review and record FREEZE FRAME and FAILED RECORDS data, and note readings. Operate vehicle within FAILURE RECORDS conditions. Monitor specified DTC information. Observe test results. If scan tool does not indicate DTC P0327 FAILED THIS IGNITION, go to «DIAGNOSTIC AIDS»(ref-12126-S41470125182000121100000). If scan tool indicates DTC P0327 FAILED THIS IGNITION, go to next step.
4. Turn ignition off. Disconnect KS. Turn ignition on. Using a DVOM, measure voltage between KS harness connector and ground. (Scheme 11) If reading is about 5 volts, go to next step. If reading is not about 5 volts, go to step 8.
5. Measure resistance of KS by connecting DVOM between KS terminal and engine block. If resistance is about 100 k/ohms, go to next step. If reading is not about 100 k/ohms, go to step 9.
6. Check KS sensor harness connector for a poor connection at sensor. If a problem was found, repair as necessary and go to next step. If connection is okay, go to step 9.
7. Connect KS. Turn ignition on. Using scan tool, monitor KS reading. Using a metal object, tap on engine lift bracket. If KS value changes, go to step 11. If no change is indicated, go to next step.
8. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Check KS signal circuit for an open or shorted condition. see scheme 1and (Scheme 11). Repair as necessary. If repair was performed, go to step 11. If open or shorted condition was not present, go to step 10.
9. Replace KS. Go to step 11.
10. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.
11. Using scan tool, select DTC and clear information. Start engine. Idle engine at normal operating temperature. Select specified DTC. Enter DTC P0327. Operate vehicle within conditions for setting DTC P0327. If scan tool indicates vehicle RAN AND PASSED, go to next step. If scan tool indicates DTC FAILED THIS IGNITION, return to step 2.
12. Using scan tool, select CAPTURE INFO and REVIEW. If any other DTCs are displayed, go to appropriate diagnostic test procedure.

CKP sensor produces 58X reference signal. PCM uses this information to calculate engine speed and CKP position. PCM compares number of 58X reference pulses to Camshaft Position (CMP) pulses. If PCM receives incorrect number of pulses, DTC P0336 will set.

Conditions required to set DTC are

1. Engine running.
2. Extra or missing pulses detected between consecutive 58X reference pulses.
3. Listed conditions detected in 10 of 100 crankshaft rotations.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Observe a voltmeter connected to 58X CKP sensor reference circuit at PCM harness connector while moving all related harnesses and connectors. A change in voltage indicates fault location. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Attempt to start engine. If engine starts and runs, go to next step. If engine does not start and run, see ENGINE CRANKS BUT WILL NOT RUN under NO START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES article.
3. Using scan tool, review and record FAILURE RECORDS information. Clear DTC. Start engine and allow it to idle for one minute. Read DTCs. If DTC P0336 resets, go to next step. If DTC does not reset, go to «DIAGNOSTIC AIDS»(ref-12126-S24542804162000121100000).
4. Disconnect PCM and CKP sensor harness connectors. Check for an open or a short to ground in CKP sensor input circuit (Yellow wire) between CKP sensor harness connector and PCM harness connector. see scheme 1and (Scheme 10). If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
5. Reconnect PCM and CKP sensor harness connectors. Using a DVOM, measure voltage at PCM harness connector terminal C5 (Yellow wire) while cranking engine. see scheme 1 If DVOM reads around 2.5 volts, go to step 8. If voltage is not as specified, go to next step.
6. Check for faulty connections at CKP sensor. If a faulty connection is found, repair as necessary. Retest system. If connections are okay, go to next step.
7. Replace CKP sensor. Perform TOOTH ERROR CORRECTION LEARN PROCEDURE. See «TOOTH ERROR CORRECTION LEARN PROCEDURE»(ref-12126-S21777065752000121100000) under PROGRAMMING. Retest system.
8. Check for faulty connections at PCM harness connector terminal C5 (Yellow wire) and C6 (Brown wire). If a faulty connection is found, repair as necessary. Retest system. If connections are okay, go to next step.
9. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition off and disconnect CKP sensor harness connector. Turn ignition on. Connect DVOM between 5-volt reference (Brown wire) and sensor ground (Green wire) terminals at CKP sensor harness connector. (Scheme 10) If DVOM reads 5 volts, go to step 5. If reading is not as specified, go to next step.
3. With ignition on, use DVOM to backprobe between PCM harness connector terminals C6 (Brown wire) and D8 (Green wire). see scheme 1 If DVOM reads 5 volts, go to next step. If reading is not as specified, go to step 9.
4. Using DVOM, check resistance of 5-volt reference (Brown wire) and sensor ground (Green wire) circuits between PCM and CKP harness connectors. (Scheme 10) If an open or short is discovered, repair circuit. Retest system.
5. Turn ignition off. Disconnect PCM and CKP sensor harness connectors. Check for an open circuit or short to ground in Yellow wire between CKP sensor harness connector and PCM harness connector terminal C5. see scheme 1and (Scheme 10). If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
6. Reconnect PCM and CKP sensor harness connectors. Using DVOM, measure voltage at PCM harness connector terminal C5 while cranking engine. If reading is about 2.5 volts, go to step 9. If voltage is not as specified, go to next step.
7. Inspect connections at CKP sensor. Repair connections as necessary. Retest system. If no problem was found, go to next step.
8. Replace CKP sensor. Perform TOOTH ERROR CORRECTION LEARN PROCEDURE. See «TOOTH ERROR CORRECTION LEARN PROCEDURE»(ref-12126-S21777065752000121100000) under PROGRAMMING. Retest system.
9. Inspect connections at PCM. Repair connections as necessary. Retest system. If no problem was found, go to next step.
10. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Camshaft Position Sensor (CMP) signal pulses are used by PCM to initiate fuel injection. CMP and CKP sensor pulses are constantly being compared to each other. PCM will set DTC P0341 if CMP sensor pulses are not in proper ratio to CKP sensor reference pulses.

Conditions required to set DTC are

1. Engine running and PCM receiving CMP reference pulses.
2. Listed condition fails for 10 occurrences within 100 test samples.

If a CKP DTC is also present, check shared ground circuit. If a fuel injector DTC is also present, check shared power supply circuit. Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Observe a voltmeter connected to CMP sensor signal circuit at PCM harness connector while moving all related harnesses and connectors. A change in voltage indicates fault location. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. Using scan tool, read and record FAILURE RECORDS data for DTC P0341. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, monitor specified DTC parameters. If scan tool displays DTC P0341 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0341 FAILED THIS IGN, see «DIAGNOSTIC AIDS»(ref-12126-S39260378742000121100000).
3. Using DVOM, backprobe PCM harness connector terminal D11 (Blue wire). see scheme 1 With sensor connected, crank engine and monitor voltage. If voltage toggles from 0 to 4 volts, go to next step. If voltage does not toggle as described, go to step 7.
4. Check for poor connection at PCM harness connector terminal D11 (Blue wire). If a problem is found, go to next step. If no problem is found, go to step 6.
5. Repair damaged PCM harness connector or terminal D11. Retest system.
6. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.
7. Disconnect CMP sensor. Turn ignition on. Measure voltage at CMP sensor harness connector between Brown wire and Green wire. (Scheme 10) If reading is about 5 volts, go to step 12. If reading is not as specified, go to next step.
8. Measure voltage between CMP sensor harness connector Brown wire and ground. If reading is about 5 volts, go to step 10. If reading is not as specified, go to next step.
9. Repair open circuit between PCM main relay and CMP sensor. See WIRING DIAGRAMS article. Retest system.
10. Measure voltage between battery positive terminal and CMP sensor harness connector Green wire. If reading is around 5 volts, go to step 12. If reading is not as specified, go to next step.
11. Repair open circuit in Green wire between PCM harness connector terminal D8 and CMP sensor harness connector. see scheme 1and (Scheme 10). Retest system.
12. Turn ignition off. Using DVOM, check continuity of Blue wire between PCM harness connector terminal D11 and CMP sensor harness connector. see scheme 1and (Scheme 10). If continuity does not exist, go to next step. If continuity exists, go to step 14.
13. Repair open circuit in Blue wire between PCM harness connector terminal D11 and CMP sensor harness connector. Retest system.
14. Turn ignition on. Check Blue wire between PCM harness connector terminal D11 and CMP sensor harness connector for short to ground or to voltage. If problem is found, go to next step. If no problem is found, go to step 16.
15. Repair open or short circuit in Blue wire as necessary. Retest system.
16. Replace CMP sensor. Retest system.

Camshaft Position Sensor (CMP) signal pulses are used by PCM to initiate fuel injection. CMP and CKP sensor pulses are constantly being compared to each other. PCM will set DTC P0342 if CMP sensor pulses are not being received by PCM.

Conditions required to set DTC are

1. Engine running.
2. PCM not receiving reference pulses from CMP once every 4 cylinders.
3. Listed condition occurs for 10 seconds.

If a CKP DTC is also present, check shared ground circuit. If a fuel injector DTC is also present, check shared power supply circuit. Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Observe a voltmeter connected to CMP sensor signal circuit at PCM harness connector while moving all related harnesses and connectors. A change in voltage indicates fault location.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. Using scan tool, read and record FAILURE RECORDS data for DTC P0342. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, monitor specified DTC parameters. If scan tool displays DTC P0342 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0342 FAILED THIS IGN, see «DIAGNOSTIC AIDS»(ref-12126-S14852542522000121100000).
3. Using DVOM, backprobe PCM harness connector terminal D11 (Blue wire). see scheme 1 With sensor connected, crank engine and monitor DVOM. If reading toggles from 0 to 4 volts, go to next step. If reading does not toggle as described, go to step 7.
4. Check for poor connection at PCM terminal D11 (Blue wire). If a problem is found, go to next step. If no problem was found, go to step 6.
5. Repair poor connection at PCM terminal D11 (Blue wire) as necessary. Retest system.
6. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.
7. Disconnect CMP sensor. Turn ignition on. Using DVOM, measure voltage at CMP sensor harness connector between Blue and Green wires. If voltage is about 5 volts, go to step 12. If voltage is not as specified, go to next step.
8. Using DVOM, measure voltage between CMP sensor harness connector Brown wire and ground. If reading is about 5 volts, go to step 10. If reading is not as specified, go to next step.
9. Repair open circuit in Brown wire between PCM harness connector terminal C6 and CMP sensor. see scheme 1and (Scheme 10). Retest system.
10. Measure voltage between battery positive terminal and CMP sensor harness connector Green wire. If reading is about battery voltage, go to step 12. If reading is not as specified, go to next step.
11. Repair open circuit in Green wire between PCM harness connector terminal D8 and CMP sensor harness connector. see scheme 1and (Scheme 10). Retest system.
12. Turn ignition off. Using DVOM, check continuity of Blue wire between PCM harness connector terminal D11 and CMP sensor. If continuity does not exist, go to next step. If continuity exists, go to step 14.
13. Repair open circuit in Blue wire between PCM harness connector terminal D11 and CMP sensor. Retest system.
14. Turn ignition on. Check for short to ground or voltage in Blue wire between PCM harness connector terminal D11 and CMP sensor. If problem is found, repair as necessary. Retest system. If no problem is found, replace CMP sensor.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Check ignition control module for poor connection or damaged terminals. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
3. Check PCM harness connector terminals C4 (Red wire) and D5 (Red/Yellow wire) for poor connections or damaged terminals. see scheme 1 If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
4. Turn ignition off. Disconnect harness connectors from PCM and ignition control module. Check for an open or shorted condition between ignition control module and both PCM harness connector terminals C4 (Red wire) and D5 (Red/Yellow wire). See WIRING DIAGRAMS article. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
5. Replace ignition control module. Retest system. If problem still exists, go to next step.
6. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

PCM tests Exhaust Gas Recirculation (EGR) valve during deceleration by momentarily commanding EGR valve on while monitoring engine MAP sensor value. PCM will illuminate MIL and store DTC P0401 if expected change in MAP sensor value is not seen under test conditions during deceleration.

Conditions required to set DTC are

1. No TP, VSS, EVAP, IAC, IAT, MAP, ECT or excessive EGR DTCs set.
2. BARO is greater than 72 kPa.
3. Engine coolant temperature is greater than 165°F (74°C).
4. System voltage is 11.5-16 volts.
5. Vehicle speed is greater than 18 MPH.
6. IAC position is steady, changing less than 5 counts.
7. A/C clutch status is unchanged.

PCM will only run EGR flow test during gradual deceleration, a closed throttle condition and with vehicle speed greater than 20 MPH. After clearing DTCs, accelerate vehicle to greater than 20 MPH, and gradually decelerate 9-12 times. Check for faulty connections or damaged harness. Inspect PCM harness connector EGR control circuit for backed-out terminal. Observe ACTUAL EGR POSITION display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location.

If EGR valve shows signs of excessive heat, check exhaust system for blockage or plugged catalytic converter. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. Start engine and allow it to idle. Using scan tool, monitor MAP signal. Quickly depress accelerator pedal halfway and release quickly, returning to idle. If scan tool showed immediate large change in MAP value, go to next step. If scan tool did not show immediate large change in MAP value, replace MAP sensor. Retest system.
3. Inspect exhaust system for modifications or leaks. If a problem is found, repair as necessary and go to step 6 . If no problem is found, go to next step.
4. Remove EGR valve and check pintle, valve and passages and adapter for excessive deposits or restriction. Check EGR valve gasket and pipes for leaks. If a problem is found, repair as necessary and go to step 6 . If no problem is found, go to next step.
5. Remove EGR inlet and outlet pipes from exhaust and intake manifolds. Inspect manifold EGR ports and pipes for blockage or damage. If a problem is found, repair as necessary and go to next step. If no problem is found, see «DIAGNOSTIC AIDS»(ref-12126-S40934450442000121100000) .
6. Read and record FAILURE RECORDS data for DTC P0401. Clear DTCs and monitor EGR TEST COUNT while operating vehicle within conditions noted in «DIAGNOSTIC AIDS»(ref-12126-S40934450442000121100000) . Monitor specified DTC parameters. If scan tool displays DTC P0401 TEST RAN AND PASSED, repair is complete. If scan tool does not display DTC P0401 TEST RAN AND PASSED, return to step 2 .

PCM closes EGR system on engine start-up to test for any flow. If PCM detects any EGR flow occurring on start-up during 2 consecutive trips, DTC P0402 will be set. DTC is a "B" code.

Conditions required to set DTC are

1. Intake air temperature is greater than 41°F (5°C).
2. Engine RPM is less than 500 RPM.
3. EGR pintle position is greater than 55 counts.

Inspect for poor connections or damaged connectors. Observe ACTUAL EGR POSITION display on scan tool while moving all related harnesses and connectors. Ensure EGR is properly mounted. Review FAILURE RECORDS data to determine vehicle mileage since DTC was last set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. Turn ignition on. Using scan tool, read and record FAILURE RECORDS data. Clear DTCs and monitor DTC information for DTC P0402 while operating vehicle as specified in «DIAGNOSTIC AIDS»(ref-12126-S21465797282000121100000) . If scan tool displays DTC P0402 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0402 FAILED THIS IGN, see «DIAGNOSTIC AIDS»(ref-12126-S21465797282000121100000) .
3. Inspect exhaust system for leaks or modification of original installed parts. Repair as necessary. If exhaust system is okay, go to next step.
4. Remove EGR valve and check pintle, valve, passages and adapter for excessive deposits or restriction. Check EGR valve gasket and pipes for leaks. If a problem is found, repair as necessary. If no problem is found, go to next step.
5. Remove EGR inlet and outlet pipes from exhaust manifold and intake manifold. Inspect manifold EGR ports and pipes for damage, restriction or blockage. Repair or replace as necessary. If no problem was found, see «DIAGNOSTIC AIDS»(ref-12126-S21465797282000121100000) .

EGR system is used to reduce NOx (oxides of nitrogen) levels. This system uses a linear EGR valve. Using inputs from various sensors, PCM controls EGR pintle position and can be monitored with scan tool. Actual EGR position should always be near commanded or desired EGR position. If PCM detects a large difference between desired and actual EGR position, DTC P0404 will be set. DTC P0404 is a type "B" code.

Conditions required to set DTC are

1. Intake air temperature is greater than 41°F (5°C).
2. EGR commanded ON (EGR position change is less than 3 percent).
3. Actual EGR position differs from desired EGR position by more than 15 percent for 5 seconds.

Inspect for poor connections or damaged connectors. Observe ACTUAL EGR POSITION display on scan tool while moving all related harnesses and connectors. Ensure EGR is properly mounted. Check for signs of restricted exhaust. Check FREEZE FRAME ECT sensor data to determine if vehicle was cold when DTC was set. Due to moisture in exhaust system, EGR valve may freeze or stick in cold climates.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. Command EGR valve percentage to 25, 50, 75 and 100 while observing EGR valve position. If actual EGR valve position follows desired EGR position, go to step 19. If EGR actual position is different than EGR desired position, go to next step.
3. Turn ignition off. Disconnect EGR valve harness connector. Turn ignition on. Using a test light connected to battery voltage, probe EGR harness connector Gray/Black wire (sensor ground). (Scheme 12) If test light illuminates, go to next step. If test light does not illuminate, go to step 5.
4. Using a test light connected to ground, probe EGR harness connector Yellow wire. Using scan tool, command EGR valve percentage to increase to 25, 50, 75 and 100. If test light illumination changes with each increase command, go to step 6. If test light illumination does not change with each increase command, go to step 7.
5. Repair open circuit or poor connection in Gray/Black wire between PCM harness connector terminal D9 and EGR valve harness connector as necessary. see scheme 1and (Scheme 12). Go to step 19.
6. Using test light connected to ground, probe EGR harness connector Yellow/Red wire. If test light illuminates, go to step 8. If test light does not illuminate, go to step 9.
7. Using scan tool, turn EGR command off. Using test light connected to ground, probe EGR harness connector Yellow wire. If test light illuminates, go to step 10. If test light does not illuminate, go to step 11.
8. Check for short to voltage in Yellow/Red wire between PCM harness connector terminal B7 and EGR harness connector. see scheme 1and (Scheme 12). Repair as necessary. Go to step 19. If no problem was found, go to step 12.
9. Using a DVOM connected to ground, probe EGR harness connector Gray/Red wire. If reading is about 5 volts, go to step 13. If reading is not as specified, go to step 14.
10. Check for short to voltage in Yellow wire between PCM harness connector terminal E5 and EGR valve harness connector. see scheme 1and (Scheme 12). Repair as necessary. Go to step 19. If short to voltage does not exist, go to step 12.
11. Using a test light connected to battery voltage, probe EGR harness connector Yellow wire. If test light illuminates, go to step 15. If test light does not illuminate, go to step 16.
12. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Go to step 19.
13. Check EGR ground circuit (Gray/Black wire) for poor connection at PCM harness connector terminal D9. see scheme 1 Repair as necessary. Go to step 19. If no problem was found, go to step 17.
14. Check for short to voltage in Gray/Red wire between PCM harness connector terminal B1 and EGR harness connector. see scheme 1and (Scheme 12). Repair as necessary. Go to step 19. If no problem was found, go to step 12.
15. Check for short to ground in Yellow wire between PCM harness connector terminal E6 and EGR harness connector. see scheme 1and (Scheme 12). Repair as necessary. Go to step 19. If no problem was found, go back to step 12.
16. Check for an open circuit or poor connection in Yellow wire at EGR valve harness connector. Repair as necessary. Go to step 19. If no problem was found, go to step 18.
17. Replace EGR valve. Go to step 19.
18. Check all PCM harness connectors for poor connections. Repair as necessary. Go to next step. If no problem was found, go back to step 12.
19. Using scan tool, clear DTCs. Start engine and idle at normal operating temperature. Operate vehicle within conditions for setting DTC P0404. See CIRCUIT DESCRIPTION. If scan tool indicates diagnostic RAN AND PASSED, system is okay. If scan tool indicates diagnostic did not pass, go to step 2.

Scheme 12

EGR system is used to reduce NOx (oxides of nitrogen) levels. This system uses a linear EGR valve. Using inputs from various sensors, PCM controls EGR pintle position and can be monitored with scan tool. Actual EGR position should always be near commanded or desired EGR position. If PCM detects a short to ground in EGR signal circuit or EGR valve sensor, DTC P0405 will be set.

Conditions required to set DTC are

1. Intake air temperature is greater than 41°F (5°C).
2. Malfunction is present for 10 seconds.

Inspect for poor connections or damaged connectors. Observe ACTUAL EGR POSITION display on scan tool while moving all related harnesses and connectors. Ensure EGR is properly mounted. Check for signs of restricted exhaust. Check FREEZE FRAME data for ECT sensor to determine if vehicle was cold when DTC was set. Due to moisture in exhaust system, EGR valve may freeze or stick in cold climates.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. Command EGR valve percentage to 25, 50, 75 and 100 while observing EGR valve position. If actual EGR valve position follows desired EGR position, go to step 15. If EGR actual position is different than EGR desired position, go to next step.
3. Turn ignition off. Disconnect EGR valve harness connector. Turn ignition on. Using a DVOM connected to ground, probe EGR harness connector Gray/Red wire. If reading is about 5 volts, go to next step. If reading is not about 5 volts, go to step 5.
4. Turn ignition off. Using fused jumper wire, connect EGR valve harness connector Gray/Red and Yellow/Red wires together. Turn ignition on. If actual EGR position reading on scan tool is 100 percent, go to step 6. If actual EGR position reading is not 100 percent, go to step 7.
5. Using a test light connected to battery voltage, probe EGR valve harness connector Gray/Red wire. If test light illuminates, go to step 8. If test light does not illuminate, go to step 9.
6. Check PCM harness connector terminals B1 (Gray/Red wire) and B7 (Yellow/Red wire) for poor connections. see scheme 1 Check Gray/Red and Yellow/Red wires for poor connections at EGR valve harness connector. (Scheme 12) Repair as necessary. Go to step 15. If no problem was found, go to step 10.
7. Using a test light connected to battery voltage, probe EGR valve harness connector Yellow/Red wire. If test light illuminates, go to step 11. If test light does not illuminate, go to step 12.
8. Check for short to ground in Gray/Red wire between PCM harness connector terminal B1 and EGR valve harness connector. see scheme 1and (Scheme 12). Repair as necessary and go to step 15. If no problem was found, go to step 13.
9. Check for an open circuit in Gray/Red wire between PCM harness connector terminal B1 and EGR valve harness connector. see scheme 1and (Scheme 12). Repair as necessary and go to step 15. If no problem was found, go to step 14.
10. Replace EGR valve. Go to step 15.
11. Check for short to ground in Yellow/Red wire between PCM harness connector terminal B7 and EGR valve harness connector. see scheme 1and (Scheme 12). Repair as necessary and go to step 15. If no problem was found, go to step 13.
12. Check for an open circuit in Yellow/Red wire between PCM harness connector terminal B7 and EGR valve harness connector. see scheme 1and (Scheme 12). Repair as necessary and go to step 15. If no problem was found, go to step 14.
13. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Go to step 15.
14. Turn ignition off. Disconnect PCM harness connectors. Check for poor connections at EGR valve circuit terminals of PCM and PCM harness connector. Repair as necessary and go to next step. If PCM and PCM harness connector terminals are okay, go to step 13.
15. Using scan tool, clear DTCs. Start engine and idle at normal operating temperature. Operate vehicle within conditions for setting DTC P0405. See «CIRCUIT DESCRIPTION»(ref-12126-S23440133502000121100000). If scan tool indicates diagnostic RAN AND PASSED, system is okay. If scan tool indicates diagnostic did not pass, go to step 2.

EGR system is used to reduce NOx (oxides of nitrogen) levels. This system uses a linear EGR valve. Using inputs from various sensors, PCM controls EGR pintle position and can be monitored with scan tool. Actual EGR position should always be near commanded or desired EGR position. If PCM detects a short to ground in EGR signal circuit or EGR valve sensor, DTC P0406 will be set. DTC P0406 is a type "A" code.

Conditions required to set DTC are

1. Intake air temperature is greater than 41°F (5°C).
2. Malfunction is present for 10 seconds.

Inspect for poor connections or damaged connectors. Observe ACTUAL EGR POSITION display on scan tool while moving all related harnesses and connectors. Ensure EGR is properly mounted. Check FREEZE FRAME ECT sensor data to determine if vehicle was cold when DTC was set. Due to moisture in exhaust system, EGR valve may freeze or stick in cold climates.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. Using scan tool, read and record FAILURE RECORDS data for DTC P0406. Clear DTCs. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, monitor specified DTC parameters. If scan tool displays DTC P0406 RAN AND PASSED, see «DIAGNOSTIC AIDS»(ref-12126-S28985285072000121100000). If scan tool does not display DTC P0406 RAN AND PASSED, go to next step.
3. Turn ignition off. Disconnect EGR valve harness connector. Turn ignition on. Using DVOM, check for voltage at EGR valve harness connector Black/Yellow wire. If reading is about 12 volts, go to step 5. If reading is not about 12 volts, go to next step.
4. Check for an open or shorted condition in Black/Yellow wire between EGR valve harness connector and ENGINE IG (15-amp) fuse. (Scheme 12) Ensure ENGINE IG (15-amp) fuse is okay. Repair as necessary. Retest system.
5. Using DVOM, check resistance of EGR solenoid between terminals "A" (Yellow wire) and "E" (Black/Yellow wire). (Scheme 12) If reading is less than 5 ohms, go to next step. If reading is greater than 5 ohms, go to step 14.
6. Check for an open or short circuit in Yellow wire between PCM harness connector terminal E6 and EGR valve harness connector. see scheme 1and (Scheme 12). Repair as necessary. Retest system. If no problem was found, go to next step.
7. Turn ignition off. Disconnect EGR valve harness connector. Turn ignition on. Observe EGR value on scan tool. If reading is zero volts and zero percent, go to step 9. If reading is not as specified, go to next step.
8. Check for an open or short circuit in Yellow/Red wire between PCM harness connector terminal B7 and EGR valve harness connector. see scheme 1and (Scheme 12). Repair as necessary. Retest system. If no problem was found, go to step 15.
9. Using DVOM, check for voltage at EGR harness connector Gray/Red wire. If reading is about 5 volts, go to step 11. If reading is not as specified, go to next step.
10. Check for open or short circuit in Gray/Red wire between PCM harness connector terminal B1 and EGR valve harness connector. see scheme 1and (Scheme 12). Repair as necessary. Retest system. If an open or shorted condition does not exist, go to next step.
11. Turn ignition off. Connect DVOM between EGR valve harness connector Gray/Red and Gray/Black wires. Turn ignition on. If reading is about 5 volts, go to step 13. If reading is not as specified, go to next step.
12. Check for an open or short circuit in Gray/Black wire between PCM harness connector terminal D9 and EGR valve harness connector. see scheme 1and (Scheme 12). Repair as necessary. Retest system. If ground circuit is okay, go to step 15.
13. Turn ignition off. Using a fused jumper wire, connect EGR valve harness connector Gray/Red and Yellow/Red wires together. Turn ignition on. Observe EGR value on scan tool. If reading is 5 volts and 100 percent, go to next step. If value is not as specified, go to step 15.
14. Replace EGR valve. Retest system.
15. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000).

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. Diagnose any other existing HO2S DTC(s) before proceeding. If no other HO2S DTCs are set, go to next step.
3. Ensure TWC is an original equipment part. Check TWC for dents, or discoloration caused by excessive heat. Ensure no internal damage or catalyst rattle exists. If a problem is found, repair as necessary and go to step 6 . If no problems are found, go to next step.
4. Check exhaust system for leaks, damage, loose or missing hardware. If a problem is found, repair as necessary and go to step 7 . If no problems are found, go to next step.
5. Ensure HO2S-2 is securely installed and that harness is not damaged or contacting exhaust. If a problem is found, repair as necessary and go to step 7 . If no problems are found, go to next step.
6. Replace TWC. Check for possible engine misfire DTCs or engine mechanical problem, and go to next step.
7. Read and record FAILURE RECORDS data for DTC P0420. Clear DTCs. Start engine and allow it to idle until cooling system temperature is greater than 140°F (60°C). Run engine (while monitoring scan tool IAC RPM control function) to maintain MAF at 7-41 grams per second for at least 2 minutes. Using scan tool, monitor TWC MONITOR TEST COUNTER while operating vehicle within conditions required to set DTC. Continue operating vehicle until TWC MONITOR TEST COUNTER reaches 49 and returns to zero 2 times. Monitor specified DTC parameters. If scan tool displays DTC P0420 TEST RAN AND PASSED, repair is complete. If scan tool does not display DTC P0420 TEST RAN AND PASSED, return to step 2 .

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. If DTC P0461, P0462 or P0463 is set, repair that DTC first. See appropriate testing procedure. Go to «DTC P0461: FUEL LEVEL SENSOR CIRCUIT RANGE PERFORMANCE»(ref-12126-S02277937902000121100000) , «DTC P0462: FUEL LEVEL SENSOR LOW INPUT»(ref-12126-S36648619902000121100000) or «DTC P0463: FUEL LEVEL SENSOR HIGH INPUT»(ref-12126-S24211498052000121100000) . If specified DTCs are not set, go to next step.
3. Perform a visual and physical inspection of fuel cap. Replace as necessary. Go to step 20 . Retest system. If fuel cap is in good condition and properly installed, go to next step.
4. Using scan tool, command EVAP canister purge control valve and vent solenoid on and off. Ensure purge valve and vent solenoid make a click when commanded on and off with scan tool. If click is heard, go to next step. If no click is heard, inspect components and verify PCM output signal to each component. See appropriate chart in PIN VOLTAGE CHARTS article.
5. Turn ignition off. Remove fuel cap. Turn ignition on. Using scan tool, read fuel tank pressure value. If reading is 1.51 volts, go to step 8 . If reading is not as specified, go to next step.
6. If battery has been disconnected, perform a visual and physical inspection of EVAP system. Repair as necessary. Record and clear DTCs from memory. Test drive vehicle. Refer to test procedures for any DTC(s) set. If no DTC sets, problem may be an intermittent condition. If battery was not disconnected, go to next step.
7. Disconnect battery. Wait at least 20 seconds, and reconnect battery. Go to step 5 . NOTE: Calibrate EVAP pressure/vacuum gauges before proceeding. See manufacturer's operating instructions.
8. Install fuel cap. Using scan tool, command EVAP vent solenoid ON (closed). Connect EVAP pressure/vacuum gauge to EVAP service port. Attempt to pressurize EVAP system to 5 in. H 2 O. If 5 in. H 2 O pressure can be achieved, go to next step. If 5 in. H 2 O pressure cannot be achieved, go to step 10 .
9. If scan tool fuel tank pressure value remains between 1.47-1.51 volts, go to step 12 . If pressure cannot be maintained, go to step 11 .
10. Disconnect fuel tank vapor line and EVAP purge line from EVAP canister. Block canister fitting for fuel tank vapor line. Connect a hand vacuum pump to canister fitting for EVAP purge line. Ensure EVAP vent solenoid is still commanded ON (closed). Apply 5 in. Hg to EVAP canister. If vacuum can be maintained, go to step 15 . If vacuum cannot be maintained, go to step 14 .
11. Perform a complete visual and physical inspection of EVAP system. Check for restricted fuel tank vapor line, and a restricted EVAP purge line. Repair as necessary. Go to step 20 . If no problems are found, go to «DIAGNOSTIC AIDS»(ref-12126-S20326557592000121100000) .
12. Disconnect vacuum line from between throttle body and EVAP canister. Connect hand vacuum to EVAP canister purge valve vacuum source. Apply 10 in. Hg to EVAP canister purge valve. Using scan tool, command EVAP purge valve ON. If vacuum is released, go to next step. If vacuum is not released, go to step 17 .
13. Connect pressure/vacuum gauge to vacuum source line. Start engine and hold speed at 2500 RPM. While observing vacuum gauge, quickly depress accelerator pedal and allow engine to return to idle. If vacuum gauge reads greater than 10 in. Hg when throttle was opened and closed, go to «DIAGNOSTIC AIDS»(ref-12126-S20326557592000121100000) . If reading was not as specified, go to step 18 .
14. Perform a visual and physical inspection of EVAP system. Check for disconnected or damaged vent hose. Check for damaged EVAP canister. Repair any damaged EVAP components as necessary. Retest system. Go to step 20 . If EVAP system components are okay, go to step 19 .
15. Perform a visual and physical inspection of EVAP system. Check for missing, damaged or defective gas cap, vapor lines or EVAP purge line. Repair as necessary. Retest system. Go to step 20 . If no problem was found, go to next step.
16. Using scan tool, command EVAP vent solenoid ON. Attempt to pressurize EVAP system, while locating leak with ultrasonic leak detector. Repair as necessary. Go to step 20 .
17. Replace EVAP canister purge valve. Go to step 20 .
18. Repair cause of no source vacuum to EVAP canister purge valve. Go to step 20 .
19. Replace EVAP vent solenoid. Go to step 20 . NOTE: Review temperature variation instructions included with EVAP Diagnostic Station pressure and vacuum gauge operating instructions before proceeding.
20. Turn ignition on. Using scan tool, command EVAP vent solenoid ON (closed). Connect EVAP pressure/vacuum gauge to EVAP service port. Attempt to pressurize EVAP system to 15 in. H 2 O. If 15 in. H 2 O pressure can be achieved and held for 2 minutes, system is okay. If pressure cannot be held, go to step 3 .

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. If DTC P0461, P0462 or P0463 is set, repair that DTC first. See «DTC P0461: FUEL LEVEL SENSOR CIRCUIT RANGE PERFORMANCE»(ref-12126-S02277937902000121100000) , «DTC P0462: FUEL LEVEL SENSOR LOW INPUT»(ref-12126-S36648619902000121100000) or «DTC P0463: FUEL LEVEL SENSOR HIGH INPUT»(ref-12126-S24211498052000121100000) . If specified DTCs are not set, go to next step.
3. Using scan tool, command EVAP canister purge control valve and vent solenoid on and off. Ensure purge valve and vent solenoid make a clicking sound when commanded on and off with scan tool. If click is heard, go to next step. If no click is heard, inspect components and verify PCM output signal to each component. See appropriate chart in PIN VOLTAGE CHARTS article.
4. Turn ignition off. Remove fuel cap. Turn ignition on. Using scan tool, read fuel tank pressure value. If reading is 1.51 volts, go to step 7 . If reading is not as specified, go to next step.
5. If battery has been disconnected, perform a visual and physical inspection of EVAP system. Repair as necessary. Record and clear DTCs from memory. Test drive vehicle. Refer to test procedures for any DTC(s) set. If no DTC sets, problem may be an intermittent condition. If battery was not disconnected, go to next step.
6. Disconnect battery. Wait at least 20 seconds. Reconnect battery and go to step 4 . NOTE: Calibrate EVAP pressure/vacuum gauges before proceeding. See manufacturer's operating instructions.
7. Install fuel cap. Using scan tool, command EVAP vent solenoid ON (closed). Connect EVAP pressure/vacuum gauge to EVAP service port. Attempt to pressurize EVAP system to 5 in. H 2 O. If 5 in. H 2 O pressure can be achieved, go to next step. If 5 in. H 2 O pressure cannot be achieved, go to step 14 . NOTE: Review temperature variation instructions included with EVAP Diagnostic Station pressure and vacuum gauge operating instructions before proceeding.
8. Turn ignition on. Using scan tool, command EVAP vent solenoid on (closed). Using EVAP pressure/vacuum gauge, pressurize EVAP system until scan tool value reads 1.47-1.51 volts. Hold pressure on system for 2 minutes. If scan tool reading decreases to less than specified value, go to next step. If scan tool reading stays within specified range, see «DIAGNOSTIC AIDS»(ref-12126-S01476560882000121100000) .
9. Disconnect fuel tank vapor line and EVAP purge line from EVAP canister. Block canister fitting for fuel tank vapor line. Connect a hand vacuum pump to canister fitting for EVAP purge line. Ensure EVAP vent solenoid is still commanded ON (closed). Apply 5 in. Hg to EVAP canister. If vacuum can be maintained, go to step 12 . If vacuum cannot be maintained, go to next step.
10. Perform a visual and physical inspection of EVAP system. Check for damaged or disconnected fuel tank vapor lines or hoses and EVAP canister. Repair as necessary. Go to step 14 . If no problems were found, go to next step.
11. Replace EVAP vent solenoid. Go to step 14 .
12. Perform a visual and physical inspection of EVAP system. Check for missing, damaged or defective gas cap, vapor lines or EVAP purge line. Repair as necessary. Go to step 14 . If no problem was found, go to next step.
13. Using scan tool, command EVAP vent solenoid ON. Using EVAP pressure/vacuum gauge, pressurize EVAP system while locating leak with ultrasonic leak detector. Repair as necessary. Go to next step.
14. Turn ignition on. Using scan tool, command EVAP vent solenoid ON (closed). Connect EVAP pressure/vacuum gauge to EVAP service port. Attempt to pressurize EVAP system to 15 in. Hg. If 15 in. Hg pressure can be achieved and held for 2 minutes, system is okay. If pressure cannot be held, go to step 3 .

PCM controls EVAP canister purge control solenoid valve through use of a control (ground) circuit. If PCM commands purge solenoid to maximum duty cycle (100 percent) and voltage remains high, or PCM commands purge solenoid to minimum duty cycle (0 percent) and voltage remains low, then DTC P0443 will be set.

Conditions required to set DTC are

1. Ignition voltage is greater than 10 volts.
2. Engine run time is greater than 32 seconds.

Check for poor connections and damaged wiring harness. Check for open or shorted circuits.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on with engine off. Using scan tool, read FAILURE RECORDS data and note parameters. Clear DTCs. Start engine and operate vehicle within FAILURE RECORDS data conditions. If scan tool indicates that DTC P0443 RAN AND PASSED, go to «DIAGNOSTIC AIDS»(ref-12126-S41916252882000121100000). If scan tool does not indicate DTC P0443 RAN AND PASSED, go to next step.
3. Turn engine off. Disconnect EVAP canister purge control solenoid. Turn ignition on. Using a DVOM, check for voltage at EVAP canister purge control solenoid harness connector Black/Yellow wire. (Scheme 13) If reading indicates 12 volts, go to step 5. If reading does not indicate 12 volts, go to next step.
4. Check for an open ENGINE IG (15-amp) fuse located in underdash fuse/relay block. Also, check for an open or short circuit in Black/Yellow wire between ENGINE IG (15-amp) fuse and EVAP canister purge control solenoid harness connector. Repair as necessary. Retest system.
5. Using DVOM, measure resistance of EVAP canister purge control solenoid. If reading is less than 5 ohms, go to next step. If reading is greater than 5 ohms, go to step 7.
6. Turn ignition off. Disconnect PCM harness connectors. Check for an open or short circuit in Brown/White wire between PCM harness connector terminal B16 and EVAP canister purge control solenoid harness connector. see scheme 1and (Scheme 13). Repair as necessary. If circuit is okay, go to step 8.
7. Replace EVAP canister purge control solenoid. Retest system.
8. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Scheme 13

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. If DTCs P0461, P0462 or P0463 are set, diagnose those DTCs first. See «DTC P0461: FUEL LEVEL SENSOR CIRCUIT RANGE PERFORMANCE»(ref-12126-S02277937902000121100000) , «DTC P0462: FUEL LEVEL SENSOR LOW INPUT»(ref-12126-S36648619902000121100000) or «DTC P0463: FUEL LEVEL SENSOR HIGH INPUT»(ref-12126-S24211498052000121100000) . If specified DTCs are not set, go to next step.
3. Using scan tool, command EVAP canister purge control valve and vent solenoid on and off. Ensure purge valve and vent solenoid make a clicking sound when commanded on and off with scan tool. If click is heard, go to next step. If no click is heard, inspect components and verify PCM output signal to each component. See PIN VOLTAGE CHARTS article.
4. Turn ignition off. Remove fuel cap. Turn ignition on. Using scan tool, read fuel tank pressure value. If reading is 1.51 volts, go to step 7 . If reading is not as specified, go to next step.
5. If battery has been disconnected, perform a visual and physical inspection of EVAP system. Repair as necessary. Record and clear DTCs from memory. Test drive vehicle. Refer to test procedures for any DTC(s) set. If no DTC sets, problem may be an intermittent condition. If battery was not disconnected, go to next step.
6. Disconnect battery. Wait at least 20 seconds. Reconnect battery and go back to step 4 . NOTE: Calibrate EVAP pressure/vacuum gauges before proceeding. See manufacturer's operating instructions.
7. Install fuel cap. Using scan tool, command EVAP vent solenoid ON (closed). Connect EVAP pressure/vacuum gauge to EVAP service port. Attempt to pressurize and hold EVAP system pressure at 5 in. H 2 O. If scan tool FUEL TANK PRESSURE reading is between 1.52-1.69 volts, go to next step. If scan tool reading is not as specified, locate leak in EVAP system using a leak detector. NOTE: Review temperature variation instructions included with EVAP Diagnostic Station pressure and vacuum gauge operating instructions before proceeding.
8. Maintain specified EVAP pressure. Using scan tool, command EVAP vent solenoid off (open) while observing pressure/vacuum gauge. If EVAP system returns to 0 in. H 2 O within 5 seconds, see «DIAGNOSTIC AIDS»(ref-12126-S31502500982000121100000) . If reading does not return as specified, go to next step.
9. Disconnect large vent hose (marked AIR) from EVAP canister. Switch EVAP Diagnostic Station to PURGE. Start engine and bring to normal operating temperature. While holding engine at 2500 RPM, observe Diagnostic Station vacuum gauge for 5 seconds. If reading remains less than 30 in. H 2 O, go to next step. If reading is not as specified, go to step 12 .
10. Inspect EVAP vent hose between EVAP canister and EVAP vent solenoid for kinks, binding or a restriction. Repair as necessary and go to step 13 . If no problem was found, go to next step.
11. Replace EVAP vent solenoid. Go to step 13 .
12. Replace EVAP canister. Go to next step.
13. Using scan tool, command EVAP vent solenoid ON (closed). Using EVAP Diagnostic Station, pressurize EVAP system to 5 in. H 2 O. Place EVAP Diagnostic Station to HOLD position. While observing pressure gauge of EVAP Diagnostic Station, command EVAP vent solenoid OFF (open). IF EVAP system pressure returns to 0 in. H 2 O within 5 seconds, system is okay. If EVAP system will not return to 0 in H 2 O, go back to step 3 .

PCM controls EVAP canister vent solenoid valve by turning solenoid ground circuit on and off. If PCM commands vent solenoid on but voltage remains at 12 volts, or if PCM commands vent solenoid off but voltage remains at zero volts, DTC P0449 will set.

Conditions required to set DTC are

1. Ignition voltage is greater than 10 volts.
2. Engine run time is greater than 32 seconds. The previous mentioned conditions are met, and one of following conditions are met for 20 tests within a 40 test sample period
3. PCM senses voltage is HIGH with EVAP canister vent solenoid commanded ON.
4. PCM senses voltage is LOW with EVAP canister vent solenoid commanded OFF.

Check for poor connections or damaged wiring harness. Check for open or shorted circuits.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on with engine off. Using scan tool, read and record FAILURE RECORDS data. Clear DTCs. Start engine and operate vehicle within noted FAILURE RECORDS data conditions. If scan tool indicates DTC P0449 RAN AND PASSED, go to «DIAGNOSTIC AIDS»(ref-12126-S11323433352000121100000). If scan tool does not indicate DTC P0449 RAN AND PASSED, go to next step.
3. Turn engine off. Disconnect EVAP canister vent valve solenoid. Turn ignition on. Using a DVOM, check for voltage at EVAP canister vent valve solenoid harness connector Black/Yellow wire. (Scheme 13) If reading indicates 12 volts, go to step 5. If reading does not indicate 12 volts, go to next step.
4. Check for an open ENGINE IG (15-amp) fuse, located in underdash fuse/relay block. Also, check for an open or short in circuit between ENGINE IG (15-amp) fuse and EVAP canister vent solenoid harness connector. Repair as necessary. Retest system.
5. Using DVOM, measure resistance of EVAP canister vent solenoid. If reading is less than 5 ohms, go to next step. If reading is greater than 5 ohms, go to step 7.
6. Turn ignition off. Disconnect PCM harness connectors. Check for an open or short circuit in Red/Blue wire between PCM harness connector terminal A15 and EVAP canister vent valve solenoid harness connector. see scheme 1and (Scheme 13). Repair as necessary. If circuit is okay, go to step 8.
7. Replace EVAP canister vent solenoid. Retest system. If DTC returns, go to next step.
8. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. Turn ignition on. Compare fuel level reading on scan tool with vehicle fuel gauge. If readings are about equal, go to next step. If readings are not about equal, go to step 5 .
3. Record fuel gauge reading. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. If vehicle fuel gauge reading changes, go to next step. If fuel gauge reading does not change, go to step 5 .
4. Turn ignition off. Reconnect PCM harness connectors. Disconnect fuel tank level sensor connector. Using fused jumper wire, connect fuel level sensor harness connector Orange/Blue wire to ground. Turn ignition on. If scan tool and fuel gauge indicate 0 percent (empty), go to next step. If scan tool and fuel gauge readings do not indicate 0 percent, go to step 6 .
5. Replace fuel tank level sensor. Go to step 7 .
6. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000) . Retest system.
7. Using scan tool, clear DTC information. Start engine and idle at normal operating temperature. Operate vehicle within conditions for setting DTC P0461. If scan tool indicates diagnostic RAN AND PASSED, system is okay. If DTC does not indicate system passed, go back to step 2 .

Scheme 14

Fuel level is an important input to PCM for enhanced evaporative system diagnosis. Fuel level input is required to gauge rate of change in air pressure in EVAP system. Enhanced evaporative system diagnostic test will not be performed when fuel level is greater than 85 percent or less than 15 percent full. If PCM detects a continuous short to ground in fuel level sensor or circuit, DTC P0462 will set.

Condition required for setting DTC is; fuel level signal voltage is less than .06 volts. Condition is met for 150 out of 200 test samples.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. Observe fuel level reading on scan tool. If reading displayed is 0-1 percent, go to step 4. If scan tool does not indicate 0-1 percent, go to next step.
3. Test fuel gauge operation. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.
4. Using DVOM, backprobe Orange/Green wire at fuel level sensor harness connector. If reading is less than.13 volt, go to next step. If reading is.13 volt or greater, go to step 6.
5. Check for an open circuit in Orange/Green wire between PCM harness connector terminal B5 and fuel level sensor harness connector. see scheme 1and (Scheme 14). If an open circuit was found, go to step 7. If no problem was found, go to next step.
6. Using DVOM connected to ground, backprobe fuel level sensor output terminal of fuel level sensor. (Scheme 14) If reading is greater than 2.9 volts, go to step 9. If reading is 2.9 volts or less, go to step 10.
7. Repair open circuit in Orange/Green wire between PCM harness connector terminal B5 and fuel level sensor harness connector. see scheme 1and (Scheme 14). Go to step 11.
8. Repair open in fuel level sensor output circuit. Go to step 11.
9. Repair short to voltage in fuel level output circuit. Go to step 11.
10. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Go to next step.
11. Using scan tool, select DTC and clear DTC information. Start engine and idle at normal operating temperature. Select specified DTC INFO for DTC set. Operate vehicle within conditions for setting DTC P0462. If scan tool indicates diagnostic RAN AND PASSED, system is okay. If DTC does not indicate system RAN AND PASSED, go back to step 2.

Fuel level is an important input to PCM for enhanced evaporative system diagnosis. Fuel level input is required to gauge rate of change in air pressure in EVAP system. Enhanced evaporative system diagnostic test will not be performed when fuel level is greater than 85 percent or less than 15 percent full. If PCM detects a continuous short to voltage in fuel level sensor or circuit, DTC P0463 will set.

Condition required for setting DTC is; fuel level signal voltage is greater than 4.94 volts. Condition is met for 150 out of 200 test samples.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. Observe fuel level reading on scan tool. If reading displayed is 99-100 percent, go to step 4. If scan tool is reading is not 99-100 percent, go to next step.
3. Test fuel gauge operation. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.
4. Turn ignition off. Using DVOM, backprobe fuel level sensor input at sensor input cavity. (Scheme 14) If reading is greater than 2.9 volts, go to next step. If reading is 2.9 volts or less, go to step 6.
5. Check for open circuit in fuel level sensor ground circuit. If an open circuit is found, go to step 7. If no problem was found, go to next step.
6. Check for open circuit in fuel level sensor ground. If a problem was found, go to step 9. If no problem was found, go to step 10.
7. Locate and repair short to voltage in fuel level input circuit. (Scheme 14) Go to step 11.
8. Locate and repair short to voltage in fuel level sensor output circuit. Go to step 11.
9. Repair open in fuel level sensor ground. (Scheme 14) Go to step 11.
10. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Go to next step.
11. Using scan tool, select DTC and clear DTC information. Start engine and idle to normal operating temperature. Select specified DTC INFO for DTC set. Operate vehicle within conditions for setting DTC P0463. If scan tool indicates diagnostic RAN AND PASSED, system is okay. If DTC does not indicate system RAN AND PASSED, go back to step 2.

Fuel level is an important input to PCM for enhanced evaporative system diagnosis. Fuel level input is required to gauge rate of change in air pressure in EVAP system. Enhanced evaporative system diagnostic test will not be performed when fuel level is greater than 85 percent or less than 15 percent full. If PCM detects a continuous open or high resistance in fuel level sensor or circuit, DTC P0462 will set.

Conditions required for setting DTC are

1. No fuel level DTCs set.
2. Fuel level is more than 3 percent.
3. Intake air temperature is more than 14°F (-10°C).
4. Engine is running.

Check for poor connection at PCM. Inspect harness and connectors for damage, backed-out terminals, improper mating, broken locks, improperly formed terminals or poor connections. Observe fuel level display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. Visually check for loose or broken harness connectors, worn or broken wires or terminals, or damaged fuel tank or fuel level sensor. Repair as necessary. If no problem was found, go to next step.
3. Remove fuel tank and inspect fuel level sensor for corrosion, rust or damage. Repair or replace as necessary. If no problem was found, go to next step.
4. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000) . Retest system.

PCM controls cooling fan low speed operation through use of a low fan relay and a control circuit. If PCM commands fan low speed operation and senses fan did not turn on, or commands fan operation off and fan continues to run, DTC P0480 will be set.

Conditions required for setting DTC are

1. Ignition voltage is greater than 10 volts.
2. Engine run time is greater than 32 seconds. Both previously listed conditions are met, and one of following conditions are met for 20 tests out of 40 test samples within a 125 millisecond period
3. PCM senses voltage is high with low speed fan off.
4. PCM senses voltage is low with low speed fan on.

Check for poor connections or damaged wire harness. Check harness connectors for backed-out, deformed or loose terminals. Check for open circuits and shorts to ground or voltage.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. Review and record scan tool FAILURE RECORDS data, then clear DTCs. Operate vehicle within FAILURE RECORDS conditions that were recorded. Monitor specified DTC information for DTC P0480. If scan tool indicates DTC P0480 RAN AND PASSED, go to «DIAGNOSTIC AIDS»(ref-12126-S19133620712001081000000). If DTC P0480 is set, go to next step.
3. Turn ignition off. Remove low fan relay from underhood fuse block. Using DVOM, check for voltage at low fan relay connector Red/White wire. (Scheme 15) If reading is about 12 volts, go to next step. If reading is not about 12 volts, check for blown ELEC FAN (30-amp) fuse. Check for open or short circuit in Red/White wire between ELEC FAN (30-amp) fuse and low fan relay. Repair or replace as necessary.
4. Start engine. Using DVOM, check for voltage at low fan relay connector Red/Green wire. If battery voltage exists, go to step 6. If battery voltage does not exist, go to next step.
5. Using DVOM, with engine running, check for voltage at PCM harness connector terminal E2 (Red/Green wire). see scheme 1and (Scheme 15). If battery voltage exists, repair open or short circuit in Red/Green wire between PCM harness connector terminal E2 and low fan relay. If battery voltage does not exist, go to step 8.
6. Turn engine off. Using DVOM, check continuity of Red/Yellow wire between PCM harness connector terminal C13 and low fan relay. see scheme 1and (Scheme 15). If continuity exists, go to next step. If continuity does not exist, repair open or short circuit in Red/Yellow wire between PCM harness connector terminal C13 and low fan relay.
7. Install low fan relay. Using a fused jumper wire, ground PCM harness connector terminal C13. Turn ignition on, engine off. If fan(s) runs at low speed, go to next step. If fan(s) does not run at low speed, replace low fan relay.
8. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Scheme 15

PCM controls cooling fan high speed operation through use of a high fan relay and a control circuit. If PCM commands fan high speed operation and senses fan did not turn on, or commands fan operation off and fan continues to run, DTC P0481 will be set.

Conditions required for setting DTC are

1. Ignition voltage is greater than 10 volts.
2. Engine run time is greater than 32 seconds. Both previously listed conditions are met, and one of following conditions are met for 20 test samples within a 40 test sample period
3. PCM senses voltage is high with high speed fan off.
4. PCM senses voltage is low with high speed fan on.

Check for poor connections or damaged wire harness. Check harness connectors for backed-out, deformed or loose terminals. Check for open circuits and shorts to ground or voltage.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. Review and record scan tool FAILURE RECORDS data, then clear DTCs. Operate vehicle within FAILURE RECORDS conditions that were recorded. Monitor specified DTC information for DTC P0481. If scan tool indicates DTC P0481 RAN AND PASSED, go to «DIAGNOSTIC AIDS»(ref-12126-S35125371502001081000000). If DTC P0481 is set, go to next step.
3. Turn ignition off. Remove hi fan relay from underhood fuse block. Using DVOM, check for voltage at hi fan relay connector Red/White wire. (Scheme 15) If reading is about 12 volts, go to next step. If reading is not about 12 volts, check for blown ELEC FAN (30-amp) fuse. Check for open or short circuit in Red/White wire between ELEC FAN (30-amp) fuse and low fan relay. Repair or replace as necessary.
4. Start engine. Using DVOM, check for voltage at hi fan relay connector Red/Green wire. If battery voltage exists, go to step 6. If battery voltage does not exist, go to next step.
5. Using DVOM, with engine running, check for voltage at PCM harness connector terminal E2 (Red/Green wire). see scheme 1and (Scheme 15). If battery voltage exists, repair open or short circuit in Red/Green wire between PCM harness connector terminal E2 and hi fan relay. If battery voltage does not exist, go to step 8.
6. Turn engine off. Using DVOM, check continuity of Red/Blue wire between PCM harness connector terminal C12 and hi fan relay. see scheme 1and (Scheme 15). If continuity exists, go to next step. If continuity does not exist, repair open or short circuit in Red/Blue wire between PCM harness connector terminal C12 and hi fan relay.
7. Install hi fan relay. Using a fused jumper wire, ground PCM harness connector terminal C12. Start engine. If fan runs at hi speed, go to next step. If fan does not run at hi speed, replace hi fan relay.
8. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

The VSS circuit uses a Hall Effect switch to inform PCM of vehicle speed.

Conditions required to set DTC are

1. Engine is running.
2. Engine coolant temperature is greater than 140°F (60°C).
3. System voltage is 10-16 volts.

Check for poor connections at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness to EVAP vent solenoid, EVAP purge solenoid and fuel tank pressure sensor for an intermittent open or short circuit.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition off. Disconnect VSS harness connector. Connect a test light to positive battery terminal. Probe VSS connector ground terminal (Black wire). (Scheme 16) If test light illuminates, go to next step. If test light does not illuminate, repair open in ground circuit as necessary. Retest system.
3. With sensor disconnected, turn ignition on. Using DVOM connected to ground, probe VSS harness connector Yellow wire. (Scheme 16) If battery voltage is present, go to next step. If battery voltage is not present, repair open or short circuit in Yellow wire between METER (15-amp) fuse and VSS. Retest system.
4. Turn ignition off. Disconnect PCM harness connectors. Using a DVOM, check continuity of Black/Yellow wire between PCM harness connector terminal D7 and VSS harness connector. see scheme 1and (Scheme 16). If continuity exists, go to next step. If continuity does not exist, repair Black/Yellow wire as necessary.
5. Measure resistance between VSS sensor body and transmission case. If resistance is greater than 10 k/ohms, repair or replace VSS as necessary. If resistance is less than 10 k/ohms, replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Scheme 16

PCM controls idle speed by adjusting an Idle Air Control (IAC) valve to a calculated RPM based on sensor inputs and actual engine RPM. PCM moves IAC pintle valve in or out to vary amount of air flowing into intake manifold, and thus decrease or increase idle RPM. PCM commands IAC in counts. A higher count allows more air to by-pass throttle plate (higher idle). When PCM detects too low of an idle speed and is unable to adjust idle speed, DTC P0506 will set.

Conditions required to set DTC are

1. NO intrusive tests being run.
2. Engine run time is more than 360 seconds.
3. No TP, VSS, ECT, EGR, MAP, IAT, misfire, low voltage, fuel system, CKP, injector, HO2S, VSS or canister purge DTCs set.
4. BARO is greater than 72.7 kPa.
5. Canister purge duty cycle is greater than zero percent.
6. Engine coolant temperature is greater than 122°F (50°C).
7. Intake air temperature is more than -40° (-40°C).
8. MAP is less than 60 kPa.
9. Ignition voltage is 9.5-16 volts.
10. Throttle is closed.
11. Engine speed is 100 RPM less than desired idle.
12. Listed conditions are met for greater than 10 seconds.

Check for poor connections at IAC valve and PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Check for restrictions, collapse or blockage in air intake system, air ducts or air filter. Check throttle body bore and IAC for excessive deposits. Check for large vacuum leak, such as incorrectly installed PCV valve or disconnected brake booster hose. Check for restricted air intake system. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Using scan tool, read DTCs. If any other DTCs are set, diagnose affected DTCs before proceeding. If no other DTCs are set, go to next step.
3. Start engine. Turn all accessories off. Using scan tool, monitor ENGINE SPEED and command engine speed up to 1500 RPM, down to 500 RPM, and up to 1500 RPM. If ENGINE SPEED remains within 50 RPM of desired RPM for each command, see «DIAGNOSTIC AIDS»(ref-12126-S29319824542000121100000). If ENGINE SPEED is not as specified, go to next step.
4. Disconnect IAC harness connector. Install IAC Noid Light (J37027A or equivalent) into IAC harness connector. With engine running, monitor noid lights while commanding engine speed up to 1500 RPM, down to 500 RPM, and back up to 1500 RPM. Both node lights should cycle Green and Red, but not OFF as RPM changes from 500 to 1500 RPM. If lights flash as specified, go to step 6. If lights do not flash as specified, go to next step.
5. Check IAC "A" high and IAC "A" low, and IAC "B" high and IAC "B" low circuits for open or shorted condition. see scheme 1and (Scheme 17). If problem is found, repair as necessary. Retest system. If no problem is found in high or low circuits, go to step 8.
6. Ensure throttle stop screw has not been tampered with. Check for stuck IAC valve or throttle linkage. Check for restrictions, collapse or blockage in air intake system, air ducts or air filter. Check throttle body bore and IAC for excessive deposits. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
7. Check for faulty connection at IAC harness connector. If faulty connection is found, repair as necessary. Retest system. If connection is okay, go to next step.
8. Using a DVOM, check IAC valve solenoids for an open, short to ground or shorted together condition. If problem was found, go to next step. If no problem was found with IAC valve solenoids, go to step 10.
9. Replace IAC valve. Retest system.
10. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Scheme 17

PCM controls idle speed with an Idle Air Control (IAC) valve to a calculated RPM based on sensor inputs and actual engine RPM. PCM moves IAC valve in or out to vary amount of airflow into intake manifold, and thus decrease or increase idle RPM. PCM commands IAC in counts. A higher count allows more air to by-pass throttle plate (higher idle). When PCM detects too high of an idle speed and is unable to adjust idle speed, DTC P0507 will set.

Conditions required to set DTC are

1. Engine run time is more than 360 seconds.
2. No TP, VSS, ECT, EGR, MAP, MAT, CKP, injector, HO2S, misfire, fuel system or canister purge DTCs set.
3. BARO is greater than 72.7 kPa.
4. Canister purge duty cycle is greater than zero percent.
5. Intake air temperature is more than -58° (-50°C).
6. Engine coolant temperature is greater than 122°F (50°C).
7. Ignition voltage is 9.5-16 volts.
8. Manifold air temperature is more than -40°F (-40°C).
9. MAP is less than 60 kPa.
10. Engine speed is at least 200 RPM less than desired idle.

Check for poor connection at IAC and PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Check for vacuum leaks. Check throttle body bore and IAC for excessive deposits. Check throttle plate for sticking. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Using scan tool, read DTCs. If any other DTCs are set, diagnose affected DTCs before proceeding. If no other DTCs are set, go to next step.
3. Start engine. Turn all accessories off. Using scan tool, monitor ENGINE SPEED and command engine speed up to 1500 RPM, down to 500 RPM, and back up to 1500 RPM. If ENGINE SPEED remains within 50 RPM of desired RPM for each command, go to «DIAGNOSTIC AIDS»(ref-12126-S23859306962000121100000). If ENGINE SPEED is not as specified, to next step.
4. Disconnect IAC harness connector. Install IAC Noid Light (J37027A) or equivalent in IAC harness connector. Monitor noid lights while commanding engine speed up to 1500 RPM, down to 500 RPM, and up to 1500 RPM. Both noid lights should cycle Green and Red, but not OFF as RPM changes from 500 to 1500 RPM. If lights flash as specified, go to step 6. If lights do not flash as specified, go to next step.
5. Check IAC "A" low and IAC "A" high, and IAC "B" low and IAC "B" high circuits for open or shorted condition. see scheme 1and (Scheme 17). If problem is found, repair as necessary. Retest system. If no problem is found, go to step 9.
6. Check for vacuum leaks. Ensure throttle stop screw has not been tampered with. Check for throttle plate or shaft binding. Check accelerator and cruise control cables for misadjustment or binding. Check for faulty, missing or incorrectly installed PCV valve. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
7. Check for faulty connection at IAC harness connector. If faulty connection is found, repair as necessary. Retest system. If connection is okay, go to next step.
8. Using a DVOM, check IAC valve solenoids for an open, short to ground or shorted together condition. If such condition exists, go to next step. If no problem is found with IAC valve solenoids, go to step 10.
9. Replace IAC valve. Retest system.
10. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

PCM monitors A/C refrigerant pressure through use of a 3-wire sensor. If PCM senses pressure falls to less than a threshold value, DTC P0532 will set.

Condition required to set DTC is

1. A/C pressure sensor is less than 5 counts (.1 volt) Condition is met for 100 test failures within a sample period of 200 sample tests.

Check for poor connections at PCM and A/C pressure sensor. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Also check for open circuits, shorts to ground and shorts to voltage.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. Review and record FAILURE RECORDS data, then clear DTCs. Operate vehicle within FAILURE RECORDS data recorded. Check for DTC P0532. If scan tool indicates that DTC P0532 RAN AND PASSED, go to «DIAGNOSTIC AIDS»(ref-12126-S19889750052000121100000). If scan tool reading is not as indicated, go to next step.
3. Turn ignition off. Disconnect A/C refrigerant pressure sensor. Start vehicle and monitor A/C pressure value. If reading holds steady at less than.1 volts, go to step 5. If reading does not hold steady at less than.1 volts, go to next step.
4. Check for a short to voltage in Green wire between A/C pressure sensor harness connector and PCM harness connector terminal B9. see scheme 1and (Scheme 18). If short to voltage is found, repair as necessary. Retest system. If no problem is found, go to step 12.
5. Check for a short to ground or an open circuit in Green wire between A/C pressure sensor harness connector and PCM harness connector terminal B9. see scheme 1and (Scheme 18). Repair as necessary. If circuit is okay, go to next step.
6. Check for open or short circuit in Red wire between A/C pressure sensor harness connector and PCM harness connector terminal A1. Repair as necessary. If circuit is okay, go to next step.
7. Turn ignition off. Using DVOM, measure voltage between A/C pressure sensor harness connector Red wire and ground. Turn ignition on. If DVOM reading is about 5 volts, go to next step. If reading is not about 5 volts, go to step 12.
8. Turn ignition off. Using a fused jumper wire, connect A/C pressure sensor harness connector Red and Green wires together. Turn ignition on. Using scan tool, observe A/C pressure sensor value. If value is about 5 volts, go to next step. If value is not about 5 volts, go to step 12.
9. Using DVOM, measure resistance across A/C pressure sensor terminals. If an open condition is found, replace A/C pressure sensor. If no problem is found, go to next step.
10. Turn ignition off. Using DVOM, connect leads between A/C pressure sensor harness connector Red and Gray/Black wires. Turn ignition on. If reading is about 5 volts, go to next step. If reading is not about 5 volts, go to step 12.
11. Replace A/C refrigerant pressure sensor. Retest system.
12. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Scheme 18

PCM monitors A/C refrigerant pressure through use of a 3-wire sensor. If PCM senses pressure drop below a threshold value, DTC P0533 will set.

Condition required to set DTC is: A/C pressure sensor is greater than 250 counts (4.88 volts) for 100 test failures within a period of 200 test samples.

Check for poor connections at PCM and A/C pressure sensor. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Also check for open circuits, shorts to ground and shorts to voltage.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on. Review and record FAILURE RECORDS data, then clear DTCs. Operate vehicle within FAILURE RECORDS data recorded. Check for DTC P0533. If scan tool indicates that DTC P0533 RAN AND PASSED, go to «DIAGNOSTIC AIDS»(ref-12126-S01945279772000121100000). If scan tool reading is not as indicated, go to next step.
3. Turn ignition off. Disconnect A/C refrigerant pressure sensor. Start vehicle and monitor A/C pressure value. If reading holds steady at less than.1 volt, go to step 5. If reading does not hold steady at less than.1 volt, go to next step.
4. Check for a short to voltage in Green wire between PCM harness connector terminal B9 and A/C pressure sensor harness connector. see scheme 1and (Scheme 18). If short to voltage is found, repair as necessary. Retest system. If no problem is found, go to next step.
5. Check for a short to ground in Green wire between PCM harness connector terminal B9 and A/C pressure sensor harness connector. see scheme 1and (Scheme 18). Repair as necessary. If no problem was found, go to next step.
6. Check for open or short circuit in Red wire between PCM harness connector terminal A1 and A/C pressure sensor harness connector. Repair as necessary. If no problem was found, go to next step.
7. Turn ignition off. Using DVOM, measure voltage between A/C pressure sensor harness connector Red wire and ground. (Scheme 18) Turn ignition on. If DVOM reading is about 5 volts, go to next step. If reading is not about 5 volts, go to step 12.
8. Turn ignition off. Using a fused jumper wire, connect A/C pressure sensor harness connector Red and Green wires together. Turn ignition on. Using scan tool, observe A/C pressure sensor value. If value is about 5 volts, go to next step. If value is not about 5 volts, go to step 12.
9. Using DVOM, measure resistance across A/C pressure sensor terminals. If an open condition is found, replace A/C pressure sensor. If no problem is found, go to next step.
10. Turn ignition off. Using DVOM, measure voltage between A/C pressure sensor harness connector Red and Gray/Black wires. (Scheme 18) Turn ignition on. If reading is about 5 volts, go to next step. If reading is not about 5 volts, go to step 12.
11. Replace A/C refrigerant pressure sensor. Retest system.
12. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

PCM monitors system voltage of ignition feed terminal to PCM. A system voltage DTC will set whenever voltage is less than a calibrated value.

Conditions required to set DTC are

1. Ignition is on.
2. System voltage is less than 11.5 during 900 test failures in 15 minutes.

If DTC sets when an accessory is operated, check for a poor connection or excessive current draw. Check for an open circuit in PCM main relay ground circuit or faulty relay. Also check for open or short circuit on PCM battery or ignition inputs.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Using DVOM, measure voltage at battery. If reading is greater than 11.5 volts, go to next step. If reading is 11.5 volts or less, charge battery before proceeding to next step.
3. Install scan tool and select IGNITION VOLTS. Place vehicle in Neutral or Park. Start engine, increase engine speed to 2000 RPM, and load electrical system (turn on headlights, blower, radio, etc.). If scan tool reads about 13.2 volts, go to next step. If reading is not as specified, see appropriate article in STARTING & CHARGING SYSTEMS.
4. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Using a DVOM, measure voltage at PCM harness connector terminals E16 and F16 (both Red/Blue wires). see scheme 1 If readings are equal to battery voltage on both circuits, check for excessive current draw with ignition off. If readings are not equal to battery voltage on both circuits, go to next step.
5. Check for poor connections at PCM harness connector terminals E16 and F16 (both Red/Blue wires). Repair as necessary. Retest system. If no problem was found, go to next step.
6. Check for an open circuit between battery and PCM harness connector terminal A4. see scheme 1 Repair as necessary. Retest system. If no problem is found, go to next step.
7. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

PCM monitors system voltage of ignition feed terminals to PCM. A system voltage DTC will set whenever voltage is greater than a calibrated value.

Conditions required to set DTC are

1. Ignition is on.
2. System voltage is greater than 16 volts during 900 test failures in 15 minutes.

Check for faulty charging system components. If DTC sets when an accessory is operated, check for a poor connection or excessive current draw.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. Using DVOM, measure battery voltage at battery. If reading is less than 16 volts, go to next step. If reading is 16 volts or more, go to step 4 .
3. Charge battery and clean battery terminals and cable connections. If voltage is more than 16 volts, replace battery. If voltage is less than 16 volts, go next step.
4. Turn all accessories off. Install scan tool and select ignition voltage parameter. Place vehicle in Park or Neutral. Start engine and increase engine speed to 2000 RPM. If scan tool reading is more than 16 volts, replace or repair generator as necessary. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. Retest system. If voltage is not more than 16 volts, go to next step.
5. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000) . Retest system.

PCM uses an Electrically Erasable Programmable Read Only Memory (EEPROM). EEPROM contains program information and calibrations required for engine, transaxle, and powertrain diagnostics operation.

If PCM detects an internal program fault (check sum error), DTC will set.

Only possible repair is PCM reprogramming or replacement.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. Reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000) . Retest system. If DTC P0601 is still present, go to next step.
3. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000) . After repair is completed, retest system.

Engine load is determined using a "speed density" method. This method is calculated using inputs from Manifold Absolute Pressure (MAP) sensor, Crankshaft Position (CKP) sensor, Intake Air Temperature (IAT) sensor and engine RPM. MAP sensor is main sensor used to calculate engine load. PCM supplies a 5-volt reference signal and a ground circuit to MAP sensor. As manifold pressure changes, MAP sensor input voltage to PCM varies from less than 2 volts at idle to greater than 4 volts at Wide Open Throttle (WOT). If PCM detects MAP sensor input voltage that is intermittently above calculated value, DTC P1106 will set.

Conditions required to set DTC are

1. No TP sensor DTCs set.
2. Engine is running.
3. TP angle is less than 2.7 percent if engine speed is less than 1000 RPM.
4. TP angle is less than 10 percent if engine speed is greater than 1000 RPM.
5. MAP sensor intermittently indicates MAP greater than 90 kPa during 64 test failures over 256 test sample period.

Check for leaking or plugged vacuum line to MAP sensor. Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Observe MAP display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Using scan tool, determine if DTC P0108 is set. If it is, diagnose DTC P0108 before proceeding. See «DTC P0108: MAP SENSOR CIRCUIT HIGH INPUT»(ref-12126-S13395480162000121100000). If DTC is not set, go to next step.
3. If DTC P0463 and/or P1121 is also set, go to step 6. If neither of these DTCs are set, go to next step.
4. Check for poor connection at MAP sensor harness connector Gray/Black wire. If problem is found, go to step 9. If no problem is found, go to next step.
5. Check for intermittent short to voltage in Gray wire between PCM harness connector terminal F8 and MAP sensor harness connector. see scheme 1and (Scheme 3). If a problem is found, go to step 10. If no problem is found, go to step 8.
6. Check for intermittent short to voltage in Gray/Red wire between PCM harness connector terminal B1, MAP and FTP sensors. see scheme 1and (Scheme 3). See If a problem is found, go to step 10. If no problem is found, go to next step.
7. Check for faulty terminal connection at PCM harness connector terminal D9 (Gray/Black wire). If problem is found, go to step 9. If no problem is found, go to next step.
8. Check for intermittent open or faulty splice in Gray/Black wire between PCM harness connector terminal D9 and MAP sensor. If a problem is found, go to step 10. If no problem is found, go to «DIAGNOSTIC AIDS»(ref-12126-S21942524592000121100000).
9. Repair or replace faulty terminal or connector at Gray/Black wire. Retest system.
10. Locate and repair intermittent open/short circuit. Retest system.

Engine load is determined using a "speed density" method. This method is calculated using inputs from Manifold Absolute Pressure (MAP) sensor, Crankshaft Position (CKP) sensor, Intake Air Temperature (IAT) sensor and engine RPM. MAP sensor is main sensor used to calculate engine load. PCM supplies a 5-volt reference signal and a ground circuit to MAP sensor. As manifold pressure changes, MAP sensor input voltage to PCM varies from less than 2 volts at idle to greater than 4 volts at Wide Open Throttle (WOT). If PCM detects MAP sensor input voltage that is intermittently below calculated value, DTC P1107 will set.

Conditions required to set DTC are

1. No TP sensor DTCs set.
2. Engine is running.
3. TP ANGLE below 0 percent when engine speed is less than 1300 RPM.
4. TP ANGLE below 5 percent when engine speed is more than 1300 RPM.
5. MAP sensor intermittently indicates MAP more than 11 kPa. Conditions are met for 64 test failures during a 256 test sample period.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Observe MAP display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Using scan tool, determine if DTC P0107 is set. If it is, diagnose DTC P0107 before proceeding. See «DTC P0107: MAP SENSOR CIRCUIT LOW INPUT»(ref-12126-S32011583042000121100000). If DTC is not set, go to next step.
3. If DTC P0462 and/or P1122 is also set, go to step 6. If either DTC is not set, go to next step.
4. Check for poor connection at MAP sensor harness connector Gray/Red wire. If a problem is found, go to step 9. If no problem is found, go to next step.
5. Check for intermittent open or short to ground in Gray wire between PCM harness connector terminal F8 and MAP sensor harness connector. see scheme 1and (Scheme 3). If problem is found, go to step 10. If no problem is found, go to step 8.
6. Check for intermittent short to ground on Gray/Red wire between PCM harness connector terminal B1, MAP sensor and FTP sensor. see scheme 1and (Scheme 3). If a problem is found, go to step 10. If no problem is found, go to next step.
7. Check for faulty connection at PCM harness connector terminal B1 (Gray/Red wire). If faulty connection is found, go to step 9. If connection is okay, go to next step.
8. Check for intermittent open or faulty splice in Gray/Red wire between PCM harness connector terminal B1, MAP sensor and FTP sensor. see scheme 1and (Scheme 3). If a problem is found, go to step 10. If no problem is found, go to «DIAGNOSTIC AIDS»(ref-12126-S32356112812000121100000).
9. Repair or replace faulty connector terminal(s). Retest system.
10. Repair circuit as necessary. Retest system.

Intake Air Temperature (IAT) sensor is a thermistor, which varies resistance based on temperature. As temperature of sensor increases, resistance decreases. High temperature will result in a low signal voltage. DTC will set when PCM senses IAT sensor voltage is intermittently excessively high.

Conditions required to set DTC are

1. Engine running for more than 4 minutes.
2. Vehicle speed is less than 20 MPH.
3. MAF less than 20 grams per second.
4. Engine coolant temperature is greater than 140°F (60°C).
5. IAT signal voltage intermittently indicates IAT less than -38°F (-39°C), about 5 volts. Conditions are met for 20 test failures within 256 test sample period.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Observe IAT display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Using scan tool, determine if DTC P0113 is set. If it is, diagnose DTC P0113 before proceeding. See «DTC P0113: IAT SENSOR CIRCUIT HIGH INPUT»(ref-12126-S20039406222000121100000). If DTC is not set, go to next step.
3. Check for a poor connection at IAT sensor harness connector Gray/Black wire. If problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
4. Check for poor connection at IAT sensor harness connector Yellow/Green wire. If problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
5. Check for intermittent open in Yellow/Green wire between PCM harness connector terminal B8 and IAT sensor harness connector. see scheme 1and (Scheme 4). Repair as necessary. Retest system. If no problem was found, go to next step.
6. Check for intermittent short to voltage in Yellow/Green wire between PCM harness connector terminal B8 and IAT sensor harness connector. Repair as necessary. Retest system. If no problem was found, go to next step.
7. Check for poor connection at PCM harness connector terminal D9. see scheme 1 If problem was found, repair as necessary. Retest system. If no problem was found, go to next step.
8. Check for intermittent open or faulty splice in Blue/Yellow wire between PCM harness connector terminal D9 and IAT sensor. see scheme 1and (Scheme 4). If a problem was found, repair as necessary. Retest system. If no problem was found, see «DIAGNOSTIC AIDS»(ref-12126-S09458613162000121100000).

Intake Air Temperature (IAT) sensor is a thermistor, which varies resistance based on temperature. As temperature of sensor increases, resistance decreases. High temperature will result in a low signal voltage. DTC will set when PCM senses IAT sensor voltage is intermittently excessively low.

Conditions required to set DTC are

1. Engine running longer than 2 minutes.
2. Vehicle speed is greater than 30 MPH.
3. IAT signal voltage intermittently indicates IAT greater than 298°F (148°C), about .10 volt, for test 20 failures within 200 test samples.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Observe IAT display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. Check for IAT sensor out of range. See IAT SENSOR RESISTANCE table under DTC P0112. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Using scan tool, record any other failed DTCs. If DTC P0112 is also set, diagnose DTC P0112 before proceeding. See «DTC P0112: IAT SENSOR CIRCUIT LOW INPUT»(ref-12126-S14790177312000121100000). If DTC is not set, go to next step.
3. Check for intermittent short to ground in Yellow/Green wire between PCM harness connector terminal B8 and IAT sensor harness connector. see scheme 1and (Scheme 4). Repair as necessary. Retest system. If no problem was found, see «DIAGNOSTIC AIDS»(ref-12126-S35070113662000121100000).

Engine Coolant Temperature (ECT) sensor is a thermistor or a variable resistor, that varies resistance based on temperature. As temperature of sensor increases, resistance decreases. High temperature will result in a low signal voltage. DTC will set when PCM sees an ECT sensor voltage intermittently less than 1.5 volt.

Conditions required to set DTC is

1. Engine running for longer than 2 minutes.
2. ECT sensor intermittently indicates ECT greater than 302°F (150°C), about .10 volt, for 20 test failures within 200 test samples.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Observe ECT display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Using scan tool, record any other failed DTCs. If DTC P0117 is also set, diagnose DTC P0117 before proceeding. See «DTC P0117: ECT SENSOR CIRCUIT LOW INPUT»(ref-12126-S24645763992000121100000). If DTC is not set, go to next step.
3. Check for intermittent short to ground in Blue/Red wire between PCM harness connector terminal E9 and ECT sensor harness connector. see scheme 1and (Scheme 5). If short to ground is found, repair as necessary. Retest system. If no short to ground is found, see «DIAGNOSTIC AIDS»(ref-12126-S24593802002000121100000).

Engine Coolant Temperature (ECT) sensor is a thermistor or a variable resistor, that varies resistance based on temperature. As temperature of sensor increases, resistance decreases. High temperature will result in a low signal voltage. DTC will set when PCM sees an ECT sensor voltage intermittently greater than 2 volts.

Conditions required to set DTC are

1. Engine running longer than 180 seconds.
2. ECT sensor intermittently indicates temperature below -38°F (-39°C), about 5 volts, for 20 test failures within 200 test samples.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Observe ECT display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Using scan tool, record any other failed DTCs. If DTC P0118 is also set, diagnose DTC P0118 before proceeding. See «DTC P0118: ECT SENSOR CIRCUIT HIGH INPUT»(ref-12126-S41524451292000121100000). If DTC is not set, go to next step.
3. Check for faulty connection at ECT sensor harness connector Blue wire. If faulty connection is found, repair as necessary. Retest system. If connection is okay, go to next step.
4. Check for faulty connection at ECT sensor harness connector Blue/Red wire. If faulty connection is found, repair as necessary. Retest system. If connection is okay, go to next step.
5. Check for intermittent open circuit in Blue/Red wire between PCM harness connector terminal E9 and ECT sensor harness connector. see scheme 1and (Scheme 5). Repair as necessary. Retest system. If no problem was found, go to next step.
6. Check for intermittent short to voltage in Blue/Red wire between PCM harness connector terminal E9 and ECT sensor harness connector. see scheme 1and (Scheme 5). Repair as necessary. Retest system. If no problem was found, go to next step.
7. Check for poor connection in Green wire at PCM harness connector terminal E8. see scheme 1 If problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
8. Check for intermittent open or faulty splice in Green wire between PCM and ECT. Repair as necessary. Retest system. If no problem is found, see «DIAGNOSTIC AIDS»(ref-12126-S25465976462000121100000).

Throttle Position (TP) sensor measures amount of throttle opening. PCM uses TP sensor information for fuel delivery calculations. TP sensor signal voltage will vary from less than one volt at closed throttle to more than 4 volts at Wide Open Throttle (WOT). DTC P1121 sets if PCM senses TP sensor voltage intermittently greater than 4.9 volts.

Conditions required to set DTC are

1. Ignition is on.
2. TP signal voltage is intermittently greater than 4.88 volts.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Observe TP SENSOR display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Using scan tool, record any other failed DTCs. If DTC P0123 is also set, diagnose DTC P0123 before proceeding. See «DTC P0123: TP SENSOR CIRCUIT HIGH INPUT»(ref-12126-S01998255502000121100000). If DTC is not set, go to next step.
3. If DTC P0463 or P1106 is also set, go to step 6. If neither of these DTCs are set, go to next step.
4. Check for poor connection at TP sensor harness connector Green wire. If problem is found, go to step 9. If no problem is found, go to next step.
5. Check for intermittent short to voltage in Blue wire between PCM harness connector terminal E8 and TP sensor harness connector. see scheme 1and (Scheme 6). If a problem is found, go to step 10. If no problem is found, go to step 8.
6. Check for intermittent short to voltage in Gray/Blue wire between PCM harness connector terminal A1 and TP sensor harness connector. see scheme 1and (Scheme 6). If a problem is found, go to step 10. If no problem is found, go to next step.
7. Check for poor connection at PCM harness connector terminal D8 (Green wire). If problem is found, go to step 9. If no problem is found, go to next step.
8. Check for intermittent open or faulty splice in Green wire between PCM harness connector terminal D8 and TP sensor. If a problem is found, go to step 10. If no problem is found, see «DIAGNOSTIC AIDS»(ref-12126-S37239818932000121100000).
9. Repair or replace faulty harness connector terminal. Retest system.
10. Locate and repair intermittent open/short circuit. Retest system.

Throttle Position (TP) sensor measures amount of throttle opening. PCM uses TP sensor information for fuel delivery calculations. TP sensor signal voltage will vary from less than one volt at closed throttle to more than 4 volts at Wide Open Throttle (WOT). DTC P1122 sets if PCM senses TP sensor voltage intermittently less than .235 volt.

Conditions required to set DTC are

1. Ignition is on.
2. TP signal voltage is intermittently less than .235 volt for .15 seconds during a 1.5-second period.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage. Observe TP SENSOR display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Using scan tool, record any other failed DTCs. If DTC P0122 is also set, diagnose DTC P0122 before proceeding. See «DTC P0122: TP SENSOR CIRCUIT LOW INPUT»(ref-12126-S35056731412000121100000). If DTC P0122 is not set, go to next step.
3. If DTC P1107 and/or P0462 is also set, go to step 6. If DTCs are not set, go to next step.
4. Check for poor connection at TP sensor harness connector Gray/Blue and Blue wires. If a problem is found, go to step 9. If no problem is found, go to next step.
5. Check for intermittent open or short to ground in Blue wire between PCM harness connector terminal E8 and TP sensor harness connector. see scheme 1and (Scheme 6). If problem is found, go to step 10. If no problem is found, go to step 8.
6. Check for intermittent short to ground in Gray/Blue wire between PCM harness connector terminal A1 and MAP or EGR Position sensors. see scheme 1and (Scheme 6). If a problem is found, go to step 9. If no problem is found, go to step 8.
7. Check for poor connection at PCM harness connector terminal A1 (Gray/Blue wire). If poor connection is found, go to step 9. If connection is okay, go to next step.
8. Check for intermittent open or faulty splice in Gray/Blue wire between PCM harness connector terminal A1 and TP sensor. If a problem is found, go to step 10. If no problem is found, see «DIAGNOSTIC AIDS»(ref-12126-S40715397842000121100000).
9. Replace faulty harness connector terminal(s). Retest system. If a driveability symptom still exists, go to TROUBLE SHOOTING - NO CODES article.
10. Repair intermittent open/short circuit in wiring harness as necessary. Retest system. If a driveability symptom still exists, go to TROUBLE SHOOTING - NO CODES article.

PCM monitors Heated Oxygen Sensor (HO2S) activity for 90 seconds after closed loop operation has begun. PCM determines if HO2S-1 is functioning properly by counting number of HO2S-1 Lean/Rich (L/R) and Rich/Lean (R/L) switches. If PCM determines that HO2S-1 did not switch enough times, DTC 1133 is set.

Conditions required to set DTC are

1. Engine coolant temperature is greater than 140°F (60°C).
2. Engine is operating in closed loop.
3. Engine running at least 2 minutes.
4. Canister purge duty cycle is greater than 2 percent.
5. MAF calculated airflow is 17-32 grams/sec.
6. Engine speed is 1500-3500 RPM.
7. All conditions are present for one second.

About 90 seconds after closed loop, PCM monitors oxygen sensor as it switches greater than and less than .45 volt. If less than 12 R/L and L/R switches are detected, DTC P1133 will be set.

Check HO2S-1 heater circuits for intermittent faults or poor connections. If HO2S-1 heater circuits are okay, replace HO2S-1. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Using scan tool, record any other failed DTCs. If any other DTCs are set, diagnose affected DTC before proceeding. If no other DTC sets, start engine and allow it to idle. Operate vehicle within conditions required to set DTC. Using scan tool, monitor specified DTC parameters. If scan tool displays DTC P1133 FAILED THIS IGN, go to next step. If scan tool does not display DTC P1133 FAILED THIS IGN, go to «DIAGNOSTIC AIDS»(ref-12126-S42030660082000121100000).
3. Using scan tool, select LAST TEST FAIL. Record any other failed DTCs. If DTC P1153 or P1154 is also set, go to step 11. If neither DTC is set, go to next step.
4. Check exhaust system for leaks. If exhaust leak is found, repair as necessary and go to step 2. If no exhaust leak is found, go to next step.
5. Visually inspect HO2S-1 for secure installation or corrosion on terminals. Check for poor connections at HO2S-1 and PCM harness connector terminals C14 (White wire) and C15 (Red wire). see scheme 1and (Scheme 7). Check for damaged wiring. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
6. Disconnect HO2S-1 connector. Using DVOM connected to ground, measure voltage at both HO2S-1 harness connector White wire and Red wire. Turn ignition on and read DVOM at each connection. If reading is 3-4 mV, go to step 9. If voltage is not as specified, go to next step.
7. Turn ignition off and check for damage to PCM harness connector terminals C14 and C15. see scheme 1 If a problem was found, repair as necessary and retest system. If no problem was found, go to next step.
8. Check for a short to voltage or ground, or an open circuit in Red or White wires between PCM harness connector and HO2S-1 harness connector. (Scheme 7) If problem was found, repair as necessary. Retest system. If no problem was found, go to next step.
9. Turn ignition off. Disconnect PCM harness connectors. Disconnect HO2S and check for short between Red and White wires between PCM and HO2S-1. If a problem was found, repair as necessary. Retest system. If no problem was found, go to next step.
10. Connect PCM and disconnect HO2S-1. Using scan tool, check voltage. If reading is.43-.47 volts, go to next step. If voltage is not as specified, go to step 12.
11. Check for fuel contamination, use of improper RTV sealant or excessive engine oil and coolant consumption. Replace affected HO2S. Retest system.
12. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

PCM reads Heated Oxygen Sensor (HO2S) activity for 90 seconds after closed loop operation has begun. During this period, PCM counts number of Lean/Rich (L/R) and Rich/Lean (R/L) switches. With this information, an average time for all transitions can be determined. PCM then divides R/L average by L/R rich average to obtain a ratio. If HO2S ratio is not within range, DTC P1134 will set.

Conditions required to set DTC are

1. No MAP, IAT, ECT, TP sensor, fuel trim, injector, misfire, CKP, EGR, or EVAP DTCs set.
2. Engine coolant temperature is greater than 140°F (60°C).
3. Vehicle operating in closed loop mode.
4. Engine running at least two minutes.
5. MAF calculated airflow is 17-32 grams/sec.
6. Canister purge duty cycle is greater than 2 percent.
7. Engine speed is 1500-3500 RPM.
8. Listed conditions are present during 1-second monitoring period.
9. About 90 seconds after closed loop, HO2S-1 transition ratio between lean-to-rich and rich-to-lean is less than .25 or greater than 4.43.

Check HO2S-1 heater circuits for intermittent faults. If HO2S-1 heater circuits are okay, replace HO2S-1. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Using scan tool, select LAST TEST FAIL. Record any other failed DTCs. If any other DTCs are set, diagnose other DTCs before proceeding. If no other DTC sets, start engine and allow it to idle. Operate vehicle within conditions required to set DTC. Using scan tool, monitor specified DTC parameters. If scan tool displays DTC P1134 FAILED THIS IGN, go to next step. If scan tool does not display DTC P1134 FAILED THIS IGN, go to «DIAGNOSTIC AIDS»(ref-12126-S40792676132000121100000).
3. Check exhaust system for leaks. If exhaust leak is found, repair as necessary. Retest system. If no exhaust leak is found, go to next step.
4. Visually inspect HO2S-1 for secure installation or corrosion on terminals. Check for poor connections at HO2S-1 harness connector and PCM harness connector terminals C14 and C15. see scheme 1and (Scheme 7). Check for damaged wiring. If a problem is found, go to step 7. If no problem is found, go to next step.
5. Disconnect HO2S-1 connector. Turn ignition on. Using DVOM connected to ground, measure voltage at both HO2S-1 harness connector White wire and Red wire. If DVOM reads 3-4 volts on each circuit, go to next step. If voltage is not as specified, go to step 8.
6. Turn ignition off. With HO2S-1 disconnected, use fused jumper wires to ground both HO2S-1 harness connector Red and White wires. Turn ignition on. If scan tool reading jumps from.01 volt to.45 volt when jumper is removed, go to step 10. If voltage does not change as specified, go to step 11.
7. Repair condition as necessary. Retest system.
8. Check for poor PCM connections or terminal damage. Repair as necessary. Retest system. If no problem is found, go to next step.
9. Repair open, grounded or shorted signal circuit. Retest system. If no problem is found, go back to step 6.
10. Remove HO2S-1. Check for fuel contamination, improper RTV sealant (White, powdery coating on sensor), and excessive engine oil or coolant consumption. Repair as necessary and go to step 13. If no problem is found, go to step 12.
11. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.
12. Replace HO2S-1. Retest system.
13. Before replacing HO2S-1, correct cause of contamination. Retest system.

When power enrichment is requested from PCM, PCM monitors HO2S reading to ensure power enrichment (heavy acceleration) has been achieved. If during power enrichment, rich exhaust is not detected by PCM, DTC 1171 will set.

Conditions required to set DTC are

1. No related DTCs are set.
2. Engine is operating in closed loop.
3. Engine coolant temperature is greater than 140°F (60°C).
4. HO2S voltage remains less than .4 volt for 3 seconds while in power enrichment mode.

A restricted fuel filter or fuel line can supply adequate amounts of fuel at idle, but may not be able to supply enough fuel during heavy acceleration. Water or alcohol in fuel may cause low HO2S voltage during acceleration. Check for faulty or plugged fuel injectors or low fuel level.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. If any other component-related DTCs are set, fix those DTCs first. If no other DTC is present, go to next step.
3. Check fuel level. Add fuel if tank is almost empty. If fuel was added, go to next step. If no additional fuel was required, go to step 5 .
4. Start vehicle and bring engine to normal operating temperature of 167-203°F (75-95°C). Increase engine speed to 1200 RPM and use scan tool to observe HO2S-1 voltage. If scan tool reading toggles between .1 and .9 volt, see «DIAGNOSTIC AIDS»(ref-12126-S11010754592000121100000) . If voltage is not as specified, go to next step.
5. Turn ignition off. Disconnect fuel pump relay. Crank engine to relieve fuel pressure. Install fuel pressure gauge. Reinstall fuel pump relay. Start engine, bring to normal operating temperature and allow it to idle. Disconnect vacuum line going to fuel pressure regulator and read pressure gauge. If pressure is 41-47 psi (2.9-3.3 kg/cm 2 ), see «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . If pressure reading is not as specified, go to next step.
6. Check for restricted fuel lines or filter. Repair as necessary and retest system. If no problem is found, go to next step.
7. Turn ignition on, engine off. Using scan tool, turn on fuel pump. With fuel pressure gauge still connected, pinch off fuel return line, not allowing fuel pressure to exceed 60 psi (4.2 kg/cm 2 ). Manipulate fuel line to increase pressure to greater than 47 psi (3.3 kg/cm 2 ). If pressure increases to greater than specification, go to «DIAGNOSTIC AIDS»(ref-12126-S11010754592000121100000) . If pressure does not rise to greater than specification, go to next step.
8. Check for faulty fuel pump, restricted fuel pump strainer, incorrect fuel pump, incorrect fuel being used or hot fuel. If any problem is found, repair as necessary. Retest system.

Crankshaft position system variation learning feature is used to calculate reference period errors caused by slight tolerance variations in crankshaft, crankshaft balancer interrupter rings, and Crankshaft Position (CKP) sensor Hall Effect switches. Calculated error allows PCM to accurately compensate for reference period variations. Crankshaft position system variation learning feature enhances ability of PCM to detect misfire events over a wider range of engine speed and load.

Note. Crankshaft position system variation learning procedure must be performed any time a change is made in CKP sensor to crankshaft relationship, or if PCM is replaced or reprogrammed.

DTC P1336 indicates that crankshaft position system variation values have not been stored in PCM and crankshaft position system variation learn procedure must be performed. Procedure is required after following service procedures have been performed, regardless of whether or not DTC P1336 is set

1. PCM replacement.
2. Engine replacement.
3. Crankshaft balancer replacement.
4. Crankshaft position sensor replacement.
5. Any engine repair(s) which disturbs crankshaft/harmonic balancer to crankshaft position sensor relationship. Conditions required for setting DTC
6. No ECT, KS, CKP, CMP or injector sensor DTCs.
7. PCM has not successfully learned crankshaft position Tooth Error Correction within 5 attempts or 3 miles.

DTC P1336 will only set if PCM has not learned crankshaft position system variation. PCM only needs to learn this variation once per life cycle of vehicle unless CKP sensor-to-crankshaft relationship is disturbed. Removing a part for inspection and then reinstalling it is considered a disturbance. A fully warmed up engine is critical to learning variation correctly. If a valid learn occurs, no other learns can be completed that ignition cycle.

If engine cuts out before specified learn procedure engine speed or at normal fuel cut-off RPM, PCM is not in learn procedure mode. Review crankshaft position system variation learning procedure and re-enable learn procedure. Verify that scan tool indicates TEST IN PROGRESS.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. Perform crankshaft position system variation learn position as follows: Install scan tool. Transaxle is in Park or Neutral. ECT at 158°F (70°C). Engage parking brake. Block vehicle drive wheels. All accessories off, start vehicle and warm to normal operating temperature. Enable crankshaft position system variation learning procedure with scan tool. Increase engine speed to 3920 RPM and release throttle as soon as engine cuts out. If scan tool indicates that crankshaft position system variation has been learned, go to step 5 . If scan tool does not indicate as specified, go to next step.
3. Attempt crankshaft position system variation learning procedures about 5 times. If crankshaft variation has not been learned, go to next step. If crankshaft variation has been learned, go to step 5 .
4. Check for problem with crank sensor to crankshaft relationship. Repair as necessary. After repairs, go to next step.
5. Using scan tool, select DTC, then CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, then SPECIFIC, then enter DTC P1336. Operate vehicle within conditions for setting this DTC. If scan tool indicates test RAN AND PASSED, go to next step. If scan tool does not indicate test RAN AND PASSED, repeat step 2 .
6. Using scan tool, select CAPTURE INFO, then REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. Install scan tool. Turn ignition on, with engine off. Using scan tool, check for ABS DTCs. If any ABS DTCs are set, go to step 6 . If no ABS DTCs are set, go to next step.
3. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. If misfire DTC is set, go to next step. If misfire DTC did not set, go to step 10 .
4. If DTC P1380 also set, go to next step. If DTC P1380 did not set, go to step 8 .
5. If any ABS DTCs also set, go to next step. If ABS DTCs did not set, go to step 9 .
6. Repair ABS system as necessary. See appropriate ANTI-LOCK article in BRAKES. After repair, go to next step.
7. If any other DTCs are set, diagnose DTCs as necessary. If no other DTCs are set, no problem is indicated at this time.
8. Repair condition causing misfire as necessary. After repair, go to step 10 .
9. Replace and reprogram PCM using appropriate equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000) . After repair is completed, go to next step.
10. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Start engine and allow it to idle. Ensure engine is at normal operating temperature. Operate vehicle within conditions required for setting this DTC. Select specified DTC function, then enter DTC P1380. If scan tool does not indicate test RAN AND PASSED, repeat step 2 .

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. Install scan tool. Turn ignition on, with engine off. Using scan tool, attempt to display ABS data. If ABS data can be displayed, go to step 4 . If ABS data cannot be displayed, go to next step.
3. Repair condition causing ABS data not to be displayed. See appropriate ANTI-LOCK article in BRAKES. If ABS data can now be displayed, go to next step. If ABS data still can not be displayed, go to step 10 .
4. Using scan tool, select CLEAR DTCS function to clear DTCs. Review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. If a misfire DTC sets, go to next step. If a misfire DTC did not set, go to step 8 .
5. If DTC P1380 also set, go to next step. If DTC P1380 did not set, go to step 7 .
6. If ABS data can be displayed, go to step 10 . If ABS data cannot be displayed, go to step 4 .
7. Repair condition causing misfire as necessary. After repair is completed, go to next step.
8. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Start engine and allow it to idle. Ensure engine is at normal operating temperature. Operate vehicle within conditions required for setting DTC. Select specified DTC function, then enter DTC P1381. If scan tool indicates test RAN AND PASSED, go to next step. If scan tool does not indicate test RAN AND PASSED, go back to step 2 .
9. If any other DTCs are set, diagnose DTCs as necessary. If no other DTCs are set, no problem is indicated at this time.
10. Replace and reprogram PCM using appropriate equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000) . After replacing PCM, go to next step.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within FAILURE RECORDS data as noted on scan tool. If scan tool displays DTC P1404 RAN AND PASSED, go to «DIAGNOSTIC AIDS»(ref-12126-S10052927332000121100000). If scan tool does not display DTC P1404 RAN AND PASSED, go to next step.
3. Turn ignition off. Disconnect EGR valve harness connector. Turn ignition on. Using a DVOM, check for voltage at EGR harness connector Black/Yellow wire. If 12 volts are present, go to step 5. If 12 volts are not present, go to next step.
4. Check Black/Yellow wire between ENGINE IG (15-amp) fuse in instrument panel fuse block and EGR harness connector. (Scheme 12) Repair as necessary. Retest system.
5. Using DVOM, measure resistance of EGR solenoid between terminals "A" (Yellow wire) and "E" (Black/Yellow wire). (Scheme 12) If reading is less than 5 ohms, go to next step. If reading is greater than 5 ohms, go to step 14.
6. Check for an open or short circuit in Yellow wire between PCM harness connector terminal E6 and EGR sensor harness connector. see scheme 1and (Scheme 12). Repair as necessary and retest system. If no problem was found, go to step 15.
7. Turn ignition off. Disconnect EGR valve electrical connector. Turn ignition on. Using scan tool, observe EGR value. If reading is 0 VOLTS - 0 percent, go to step 9. If reading is not as specified, go to next step.
8. Check for an open or short circuit in Yellow/Red wire between PCM harness connector terminal B7 and EGR valve sensor harness connector. see scheme 1and (Scheme 12). Repair as necessary and retest system. If no problem was found, go to step 15.
9. Turn ignition on. Using a DVOM, measure voltage at EGR valve harness connector Gray/Red wire. (Scheme 12) If reading is about 5 volts, go to step 11. If reading is not about 5 volts, go to next step.
10. Check for open or short circuit in Gray/Red wire between PCM harness connector terminal B1 and EGR valve sensor harness connector. (Scheme 12) Repair as necessary and retest system. If no problem was found, go to next step.
11. Turn ignition off. Connect DVOM between EGR valve harness connector Gray/Red and Gray/Black wires. (Scheme 12) Turn ignition on. If reading is about 5 volts, go to step 13. If reading is not about 5 volts, go to next step.
12. Check for an open or short circuit to ground in Gray/Black wire between PCM harness connector terminal D9 and EGR valve sensor harness connector. Repair as necessary and retest system. If no problem was found, go to step 15.
13. Turn ignition off. Connect a fused jumper wire between EGR valve harness connector Gray/Red and Yellow/Red wires. Observe EGR value on scan tool. If reading indicates 5 VOLTS - 100 percent, go to next step. If reading is not as specified, go to step 15.
14. Replace EGR valve. Retest system.
15. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. Turn ignition on, engine off. Remove gas cap. Using scan tool, read FUEL TANK PRESSURE. If scan tool displays 1.51 volts, go to next step. If scan does not display 1.51 volts, go to «DTC P0440: EVAP SYSTEM MALFUNCTION»(ref-12126-S14511261462000121100000) .
3. Reinstall gas cap. Disconnect rubber hose at vapor canister that goes to purge solenoid valve. Connect EVAP Diagnostic Station (J41413) or equivalent. Using scan tool, command EVAP vent solenoid ON (closed). Pressurize EVAP system until scan tool FUEL TANK PRESSURE reads 1.52-1.60 volts. If FUEL TANK PRESSURE holds specified value, go to next step. If FUEL TANK PRESSURE does not hold specified value, go to step 6 .
4. Disconnect EVAP Diagnostic Station (J41413) and plug hose end. Disconnect rubber hose at vacuum source. Connect a vacuum pump to hose. Apply 15 inches of H 2 O. Observe FUEL TANK PRESSURE on scan tool. If FUEL TANK PRESSURE reading holds between 1.47-1.51 volts, go to step 6 . If FUEL TANK PRESSURE does not hold at specified value, go to next step.
5. Replace EVAP purge solenoid valve. Retest system.
6. Check for leaking, kinked or pinched EVAP system hoses. Ensure hoses are routed properly. Check for leaking Vent Solenoid Valve or clogged filter. Repair any problems found. If no problems were found, go to next step.
7. Start engine. Remove fuel filler cap. Using scan tool, command EVAP vent solenoid ON (closed) and EVAP purge solenoid OFF (0%). Replace fuel filler cap. Run engine at 2500 RPM while monitoring FUEL TANK VACUUM on scan tool. If reading remains at 30-40 percent, repair is complete. If reading does not maintain as specified, go to «DIAGNOSTIC AIDS»(ref-12126-S23057017952000121100000) .

PCM controls A/C compressor clutch operation by turning on ground circuit for A/C compressor relay. If PCM commands A/C compressor clutch ON but circuit voltage remains high, or if PCM commands A/C compressor clutch OFF but circuit voltage remains low, DTC P1546 will be set.

Check for poor connections at A/C compressor clutch and PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, read and record FAILURE RECORDS data. Clear DTCs. Operate vehicle within FAILURE RECORDS data as noted on scan tool. If scan tool displays DTC P1546 RAN AND PASSED, go to «DIAGNOSTIC AIDS»(ref-12126-S22966111592000121100000). If scan tool does not display DTC P1546 RAN AND PASSED, go to next step.
3. Turn ignition off. Remove A/C compressor clutch relay from underhood fuse/relay block. Turn ignition on. Using DVOM, check for voltage at both ignition feed terminals (Brown wires) of A/C compressor clutch relay plug-in. (Scheme 19) If voltage readings are around 12 volts at both terminals, go to step 5. If voltage is not as specified, go to next step.
4. Check for open or short circuit in Brown wires between A/C compressor clutch relay plug-in and A/C fuse (10-amp) located in underhood fuse/relay block. (Scheme 19) Repair as necessary. Retest system.
5. Turn ignition off. Disconnect PCM harness connectors. Check for open or short circuit in Green/Red wire between PCM harness connector terminal B14 and A/C compressor relay. see scheme 1and (Scheme 19). Repair as necessary. If no problem was found, go to next step.
6. Reinstall relay. Using a fused jumper wire, ground PCM harness connector terminal B14 (Green/Red wire). see scheme 1 Turn ignition on. If A/C compressor turns on, go to step 9. If A/C compressor does not turn on, go to next step.
7. Turn ignition off. Check for open or short circuit in Brown/Yellow wire between A/C compressor clutch and A/C compressor relay. (Scheme 19) Repair as necessary. If no problem was found, go to next step.
8. Replace A/C compressor clutch relay. Retest system.
9. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Scheme 19

Serial Peripheral Interface (SPI) communication is used internally by PCM to send messages between PCM and Transmission Control Module (TCM). Each message contains a check sum value. Both PCM and TCM will compare check sum value to a predetermined calculated value. If check sums do not match, DTC P1618 will set.

Diagnostic Procedure

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. Check to ensure that EEPROM calibration is most recent version available. See «EEPROM PROGRAMMING PROCEDURE»(ref-12126-S05806276862000121100000) under PROGRAMMING. If EEPROM calibration is most recent version available, go to step 4 .
3. Reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000) . Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . If DTC P1618 resets, go to next step.
4. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000) . Retest system.

PCM monitors unexpected PCM reset. This does not turn on MIL, but does store DTC P1625. This indicates clock, or COP (Computer Operating Properly) has reset.

If P1625 is stored alone, no diagnosis is needed. Use scan tool to clear DTC.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. Start engine and allow it to idle. Using scan tool, select DTC INFO. If scan tool indicates that DTC P1625 has failed, go to next step. If scan tool does not indicate that DTC P1625 has failed, clear DTCs.
3. Turn ignition on. Using scan tool, clear DTC P1625. Start engine and allow it to idle. On scan tool, select DTC INFO for specified DTC. If scan tool indicates that DTC P1625 has failed, go to next step. If scan tool does not indicate that DTC P1625 has failed, clear DTCs.
4. Inspect vehicle for installation of any aftermarket components, such as transceiver stereos or alarm systems. If they are incorrectly installed, PCM may be influenced by emitted EMI (electromagnetic interference). Reposition components away from PCM. Retest system.

PCM monitors 5 volt reference signal when ignition is on. If PCM senses an analog to digital (A/D) conversion error within PCM, DTC P1627 will be set.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000) . After performing OBD-II system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, read and record FAILURE RECORDS data. Clear DTCs. Operate vehicle within FAILURE RECORDS data as noted on scan tool. If scan tool displays DTC P1627 RAN AND PASSED, go to «DIAGNOSTIC AIDS»(ref-12126-S39848985772000121100000) . If scan tool does not display DTC P1627 RAN AND PASSED, go to next step.
3. Check all 5 volt reference circuits for open circuits, short to ground or to voltage. See WIRING DIAGRAMS article. Repair as necessary. If no problem was found, go to next step.
4. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000) . Retest system.

PCM monitors 5 volt reference signal circuit when ignition is on. If PCM senses voltage above 5.12 volts or below 4.88 volts, DTC P1635 will be set.

Check for poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage.

1. Perform OBD-II system check. See «ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK»(ref-12126-S06180705522001050100000). After performing OBD-II system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within FAILURE RECORDS data as noted on scan tool. If scan tool displays DTC P1635 RAN AND PASSED, go to «DIAGNOSTIC AIDS»(ref-12126-S20913506252000121100000). If scan tool does not display DTC P1635 RAN AND PASSED, go to next step.
3. Check all 5 volt reference circuits for open circuits, short to ground or to voltage. (Scheme 20) Repair as necessary. If no problem was found, go to next step.
4. Replace and reprogram PCM using required equipment. See «PROGRAMMING»(ref-12126-S29289744022000121100000). Retest system.

Scheme 20