Engine Controls - Tests W/codes: Diagnosis Isuzu Trooper II

ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK

The On-Board Diagnostic II (OBD-II) System Check is the starting point for any driveability complaint diagnosis. Before any DTC(s) are retrieved, perform a visual underhood inspection checking battery and grounds for clean and tight connections. Check for poor connections or damage to wiring harness and electrical connectors. Check for corroded terminals or corrosion build-up on any connection. Repair as necessary. The OBD-II system check is an organized approach to identifying problems created by an electronic engine control system malfunction.

Use of Tech 2 scan tool is required to perform ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK. To reprogram EEPROM or to program PCM after it has been replaced, see COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION section.

Note. To identify component terminals and wire colors, see appropriate wiring diagram in WIRING DIAGRAMS article.

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

1. Turn ignition on with engine off. Verify Malfunction Indicator Light (MIL) is on. If MIL is on, go to next step. If MIL is not on, go to BASIC TESTING article.
2. Turn ignition off. Install Tech 2 scan tool. Turn ignition on. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, verify scan tool is properly installed. If scan tool is properly installed, go to step 8 .
3. Using scan tool, command MIL OFF. If MIL turns off, go to next step. If MIL does not turn off, go to BASIC TESTING article.
4. Start engine. If engine starts and continues to run, go to next step. If engine will not run, go to BASIC TESTING article.
5. Using scan tool, check if any DTCs have been set. If any DTCs are set, go to next step. If no DTCs are set, go to step 7 .
6. Are 2 or more of the following DTC(s) stored? P0107 P0108 P0113 P0118 P0122 P0123 P0712 P1392 P1406 If 2 or more of these codes are stored, go to BASIC TESTING article. If a single DTC is stored, go to appropriate DTC test under DIAGNOSTIC TESTS in appropriate TESTS W/CODES article.
7. Compare PCM data values displayed to typical engine scan data values. See appropriate SCAN TOOL DATA VALUES table under PIN VOLTAGE (VALUE) TESTS in PIN VOLTAGE CHARTS article. If values displayed are normal or close to typical values, OBD-II system check is complete. If driveability problem still exists, go to TESTS W/O CODES article. If values are not correct, go to I - SYSTEM & COMPONENT TESTS article.
8. Turn ignition off. Disconnect PCM connectors. Turn ignition on with engine off. Check for open or short in class 2 data circuit (Orange/Green wire) between Data Link Connector (DLC) terminal No. 2 and PCM 32-pin connector C-1, terminal B13. Also check for open or short in ignition feed circuit (Green/White wire) between DLC terminal No. 16 and dash fuse box. Also check for open in ground circuit (Black wire) to DLC terminal No. 4. If problem is found, repair as necessary and return to step 2 . If no problem is found, go to next step.
9. Attempt to reprogram EEPROM. Programming PCM/EEPROM requires the use of a scan tool and special manufacturer equipment. Attempt to display PCM data on scan tool. If data is now displayed, return to step 2 . If data is not displayed, go to next step.
10. Replace PCM. Program PCM. After repair, return to step 2 .

DIAGNOSTIC TROUBLE CODE DEFINITIONS

Note. If any DTCs not listed here are displayed by a scan tool, the scan tool data may be faulty. Notify the scan tool manufacturer of any DTCs displayed that are not included in the following.

DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION

DIAGNOSTIC TESTS

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

Note. If PCM requires replacement, PCM must be reprogrammed using a Tech 1 or other OBD-II compatible scan tool.

Diagnostic Aids

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation. Also, check for vacuum or PCV system leaks, incorrect PCV valve, engine oil dipstick not fully seated or engine oil filler cap loose or missing.

1. Perform On-Board Diagnostic (OBD) System Check. See «BASIC TESTING»(ref-16258) article. Go to next step.
2. Turn ignition on, with engine off. Using scan tool, select MAP from ENGINE 1 DATA LIST function. If MAP value is more than 85 kPa (sea level), go to next step. If not, go to step 19).
3. Remove MAP sensor from intake manifold, leaving harness connector connected. Install a hand-held vacuum pump to MAP sensor. Observe MAP sensor reading on scan tool while applying vacuum. Each one in. Hg applied should result in 3-4 kPa drop. Value should change smoothly with each increase in vacuum. If MAP value changed smoothly without any erratic reading, go to step 19). If reading is erratic, go to next step.
4. Apply up to 20 in. Hg to MAP sensor. If MAP sensor reading is 34 kPa or less, go to next step. If not, go to step 19).
5. Remove vacuum source from MAP sensor. If MAP sensor reading returns to original value, go to next step. If reading does not return to original value, go to step 19).
6. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME and/or FAILURE RECORDS data and note parameters. Turn ignition off for about 15 seconds. Start engine and operate vehicle within conditions required for this diagnostic to run, and as close to conditions recorded in FREEZE FRAME/FAILURE RECORDS as possible. Select DTC function and enter DTC P0101. If scan tool indicates that this test failed this ignition, go to next step. If scan tool does not indicate that this test failed this ignition, see «DIAGNOSTIC AIDS»(ref-16268-S29951165162001010800000) .
7. Check for blockage in MAF sensor inlet screen, intake manifold leak, vacuum leak at throttle body, leak at EGR valve flange and pipes, or faulty PCV valve. Repair or replace as necessary. After repairs, go to step 21). If no problem is found, go to next step.
8. Turn ignition off. Disconnect MAF sensor connector. Turn ignition on, with engine off. Using DVOM, check voltage between MAF sensor signal circuit and ground. If DVOM reads about 5 volts, go to next step. If not, go to step 10).
9. Connect test light between MAF sensor ignition feed circuit and ground circuit at sensor harness connector. If test light illuminates, go to step 13). If test light does not illuminate, go to step 12).
10. If voltage is less than 4.5 volts, go to step 14). If voltage is more than 4.5 volts, go to next step.
11. Turn ignition off. Disconnect PCM harness connector. Turn ignition on, with engine off. Using a DVOM, check voltage between MAF sensor signal circuit and ground. If voltage is zero volts, go to step 20). If not, go to step 17).
12. Connect a test light between MAF sensor ignition feed circuit and chassis ground. If test light illuminates, go to step 15). If test light does not illuminate, go to step 16).
13. Check for poor connection at MAF sensor harness terminal. Repair or replace as necessary. After repairs, go to step 21). If connection is okay, go to step 18).
14. Check MAF signal circuit between PCM and MAF sensor for open, short to ground or short to MAF ground circuit. Repair open or shorted circuit. After repairs, go to step 21). If circuits are okay, go to step 20).
15. Locate and repair open in ground circuit to MAF sensor. After repairs, go to step 21).
16. Locate and repair open in ignition feed circuit to MAF sensor. After repairs, go to step 21).
17. Locate and repair short to voltage in MAF sensor signal circuit. After repairs, go to step 21).
18. Replace MAF sensor. After replacing MAF sensor, go to step 21).
19. Replace MAP sensor. After replacing MAP sensor, go to step 21).
20. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
21. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select SPECIFIC DTC, then enter DTC P0101. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2).
22. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation. Also, a plugged or restricted air intake can cause intermittent failure.

1. Perform On-Board Diagnostic (OBD) System Check. See «BASIC TESTING»(ref-16258) article. Go to next step.
2. Start engine and allow it to reach normal operating temperature. With engine at idle, monitor MAF FREQUENCY parameter on scan tool. If display is less than 1000 Hz, go to next step. If display is 1000 Hz or greater, go to step 5).
3. With ignition on and engine off, review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0102 is set, go to next step. If DTC P0102 is not set, see «DIAGNOSTIC AIDS»(ref-16268-S03448201392001010800000) .
4. Turn ignition off. Disconnect MAF sensor harness connector. Turn ignition on. Using a voltmeter, measure voltage between ground and MAF sensor signal circuit at connector. If reading is 5 volts, go to next step. If reading is not as specified, go to step 8).
5. Using a test light, check for voltage between sensor ground circuit and voltage supply circuit at MAF sensor harness connector. If test light comes on, go to step 13). If test light does not come on, go to next step.
6. Using a test light, check for voltage between ground and voltage supply circuit at MAF sensor connector. If test light comes on, go to step 12). If test light does not come on, go to next step.
7. Check for poor connection at MAF sensor. Repair as necessary. Retest system. If connections are okay, go to step 13).
8. Turn ignition off. Disconnect PCM harness connector related to MAF sensor circuit. Turn ignition on. Using a voltmeter, measure voltage between ground and MAF signal terminal at PCM. If reading is less than 4 volts, go to next step. If reading is not as specified, go to step 11).
9. Turn ignition off. Disconnect White PCM harness connector. Disconnect MAF sensor connector. Turn ignition on. Using a voltmeter, check MAF sensor signal circuit for short to voltage supply circuit. Repair as necessary. Retest system.
10. Turn ignition off. Disconnect White PCM harness connector. Using an ohmmeter, check sensor signal circuit between MAF sensor harness connector and PCM for an open, short to ground or short to sensor ground circuit. Repair as necessary. Retest system. If wire is okay, go to step 13).
11. Locate and repair open in sensor ground circuit between MAF sensor harness connector and PCM. Retest system.
12. Locate and repair open in voltage supply circuit between MAF sensor harness connector and PCM. Retest system.
13. Replace MAF sensor. Retest system. If DTC P0102 resets, replace PCM. Retest system.

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation. Also, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform On-Board Diagnostic (OBD) System Check. See «BASIC TESTING»(ref-16258) article. Go to next step.
2. Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0103 is set, go to next step. If DTC P0103 is not set, check for an intermittent problem, see «DIAGNOSTIC AIDS»(ref-16268-S16143849862001010800000) .
3. Start engine and allow it to reach normal operating temperature. With engine at idle, monitor MAF FREQUENCY parameter on scan tool. If display is greater than 9500 Hz, go to next step. If display is 9500 Hz or less, go to step 7).
4. Turn ignition off. Disconnect MAF sensor harness connector. Start engine and let idle. Using scan tool, monitor MAF FREQUENCY parameter. If display is zero Hz, go to next step. If display is not zero Hz, go to step 6).
5. Replace MAF sensor. Retest system. If DTC P0103 resets, replace PCM. If DTC P0103 does not reset, repair is complete.
6. Check MAF sensor harness for incorrect routing near high voltage components (solenoids, relays or motors). Repair as necessary. If MAF sensor harness is okay, replace PCM. Retest system.
7. With engine at idle, monitor MAF FREQUENCY parameter on scan tool. Snap throttle wide open and release while observing scan tool display. If display reading was greater than 9500 Hz, go to step 5). If display reading was not as specified, replace PCM. Retest system.

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation. Also, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform On-Board Diagnostic (OBD) System Check. See «BASIC TESTING»(ref-16258) article. Go to next step.
2. Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0106 is set, go to step 4). If DTC P0106 is not set, go to next step.
3. Check for the following conditions: MAP sensor seal missing or damaged. Vacuum hoses disconnected, damaged or misrouted. Intake manifold leaks. Vacuum leaks at throttle body or EGR valve and/or piping. PCV valve improperly installed, damaged or missing. Repair as necessary. Retest system. If no problems are found, check for an intermittent problem, see «DIAGNOSTIC AIDS»(ref-16268-S42596772572001010800000) .
4. Turn ignition off. Disconnect MAP sensor harness connector. Turn ignition on. Observe MAP sensor parameter on scan tool. If display is about 11 kPa, go to next step. If display is not as specified, go to step 13).
5. Connect a test light between battery positive terminal and sensor signal circuit at MAP sensor harness connector. If display on scan tool is about 105 kPa, go to next step. If display is not as specified, go to step 9).
6. Using a fused jumper wire, connect voltage reference circuit and signal circuit together at MAP sensor harness connector. If display on scan tool is about 104 kPa, go to next step. If display is not as specified, go to step 8).
7. Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check MAP sensor ground circuit for high resistance, open or poor connection. Repair as necessary. Retest system. If wire is okay, go to step 11).
8. Turn ignition off. Using an ohmmeter, check MAP sensor voltage reference circuit for high resistance, open or poor connection. Repair as necessary. Retest system. If wire is okay, go to step 10).
9. Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check MAP sensor signal circuit for high resistance, open or poor connection. Repair as necessary. Retest system. If wire is okay, go to next step.
10. Check MAP sensor signal circuit for poor connection at PCM. Repair as necessary. If wire is okay, replace PCM. Retest system.
11. Check for poor connection at MAP sensor. Repair as necessary. If connection is okay, replace MAP sensor. Retest system.
12. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Using a voltmeter, check MAP sensor signal circuit for a short to battery voltage or voltage reference circuit. Repair as necessary. If wire is okay, replace PCM. Retest system.

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation.

If other DTC(s) are set that share same ground and/or 5-volt reference circuit, check for faulty connections or wiring. PCM's 5-volt reference circuits are internally connected within PCM. If all MAP sensor circuits are okay, check related 5-volt reference circuits. If it is determined that DTC is intermittent, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform On-Board Diagnostic (OBD) System Check. See «BASIC TESTING»(ref-16258) article. Go to next step.
2. Turn ignition on. With throttle fully closed, observe MAP sensor parameter on scan tool. If display is 11 kPa at sea level, go to step 4). If display is not as specified, go to next step.
3. Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0107 is set, go to next step. If DTC P0107 is not set, check for an intermittent problem, see «DIAGNOSTIC AIDS»(ref-16268-S23038204722001010800000) .
4. Turn ignition off. Disconnect MAP sensor harness connector. Using a fused jumper wire, connect sensor voltage reference circuit and sensor signal circuit together at MAP sensor harness connector. Turn ignition on. Observe MAP sensor parameter on scan tool. If display is about 5 volts and 104 kPa, replace MAP sensor. Retest system. If display is not as specified, go to next step.
5. Remove jumper wire. Connect a test light between battery positive terminal and sensor signal circuit at MAP sensor harness connector. If display on scan tool is about 5 volts and 104 kPa, go to next step. If display is not as specified, go to step 8).
6. Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check voltage reference circuit for an open or short to ground. Repair as necessary. Retest system. If wire is okay, go to next step.
7. Check voltage reference circuit for poor connection at PCM. Repair as necessary. If connection is okay, replace PCM. Retest system.
8. Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check MAP sensor signal circuit for an open, short to ground or short to sensor ground circuit. Repair as necessary. Retest system. If wire is okay, go to next step.
9. Check MAP sensor signal circuit for a poor connection at PCM or MAP sensor. Repair as necessary. If wire is okay, replace PCM. Retest system.

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation. If it is determined that DTC is intermittent, performing DTC P1108 diagnostics may isolate cause of fault.

1. Perform On-Board Diagnostic (OBD) System Check. See «BASIC TESTING»(ref-16258) article. Go to next step. NOTE: If idle is rough or unstable, repair idle problem first. See «TESTS W/O CODES»(ref-16269) article.
2. Start engine and allow it to reach normal operating temperature. With engine at idle, note MAP sensor value on scan tool. If display is greater than 90 kPa, go to step 4). If reading is not as specified, go to next step.
3. Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0108 is set, go to next step. If DTC P0108 is not set, check for an intermittent problem, see «DIAGNOSTIC AIDS»(ref-16268-S04894607822001010800000) .
4. Turn ignition off. Disconnect MAP sensor harness connector. Turn ignition on. Note MAP sensor voltage on scan tool. If display is zero volts and 11 kPa, go to next step. If display is not as specified, go to step 6).
5. Using a test light connected to ground, probe MAP sensor ground circuit. If test light comes on, go to step 7). If test light does not come on, go to step 9).
6. Using a voltmeter, check MAP sensor signal circuit for a short to battery voltage or voltage reference circuit. Repair as necessary. If wire is okay, replace PCM. Retest system.
7. Check for poor ground circuit connection at MAP sensor harness connector. Repair as necessary. Retest system. If connection is okay, go to next step.
8. Check for restricted or leaking vacuum hose to MAP sensor. Repair as necessary. If vacuum supply is okay, replace MAP sensor. Retest system.
9. Check for poor MAP sensor ground circuit connection at PCM. Repair as necessary. Retest system. If connection is okay, go to next step.
10. Turn ignition off. Using an ohmmeter, measure resistance between MAP sensor ground circuit at MAP sensor harness connector and chassis ground. If resistance is greater than 5 ohms, repair open or poor connection. If MAP sensor ground is okay, replace PCM. Retest system.

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation. If it is determined that DTC is intermittent, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform On-Board Diagnostic (OBD) System Check. See «BASIC TESTING»(ref-16258) article. Go to next step.
2. Turn ignition on. Using scan tool, monitor IAT sensor parameter. If display is greater than 283°F (148°C), go to step 4). If display is not as specified, go to next step.
3. Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0112 is set, check resistance of IAT sensor at specified temperatures. See «INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE»(ref-16268-S20430258202001010800000) . Replace IAT sensor if it does not test as specified. If DTC P0112 is not set, check for an intermittent problem, see «DIAGNOSTIC AIDS»(ref-16268-S24273276142001010800000) . INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE Temperature °F (°C) Ohms -40 (-40) 100,700 -22 (-30) 52,700 5 (-15) 21,450 23 (-5) 12,300 41 (5) 7280 59 (15) 4450 77 (25) 2796 95 (35) 1802 113 (45) 1188 140 (60) 667 176 (80) 332 212 (100) 177
4. Turn ignition off. Disconnect IAT sensor harness connector. Turn ignition on. Observe IAT parameter on scan tool. If display is less than -36°F, replace IAT sensor. Retest system. If display is not as specified, go to next step.
5. Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check IAT sensor signal circuit for short to ground. Repair as necessary. If wire is okay, replace PCM. Retest system.

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation.

If other DTC(s) are set that share same ground and/or 5-volt reference circuit, check for faulty connections or wiring. PCM 5-volt reference circuits are internally connected within PCM.

If it is determined that DTC is intermittent, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform On-Board Diagnostic (OBD) System Check. See «BASIC TESTING»(ref-16258) article. Go to next step.
2. Turn ignition on. Using scan tool, monitor IAT sensor parameter. If display is less than -36°F (-38°C), go to step 4). If display is not as specified, go to next step.
3. Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0113 is set, check resistance of IAT sensor at specified temperatures. See «INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE»(ref-16268-S20430258202001010800000) in DTC P0112. Replace IAT sensor if it does not test as specified. If DTC P0113 is not set, check for an intermittent problem, see «DIAGNOSTIC AIDS»(ref-16268-S25678996432001010800000) .
4. Turn ignition off. Disconnect IAT sensor harness connector. Using a fused jumper wire, connect terminals of IAT sensor harness connector together. Turn ignition on. Observe IAT sensor parameter on scan tool. If display is 284°F (140°C), go to step 6). If display is not as specified, go to next step.
5. Jumper IAT sensor signal circuit to ground. If display on scan tool is 284°F (140°C), go to step 7). If display is not 284°F (140°C), go to step 8).
6. Check for poor connections at IAT sensor harness connector. Repair as necessary. If connections are okay, replace IAT sensor. Retest system.
7. Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check IAT sensor ground circuit for an open. Repair as necessary. Retest system. If wire is okay, go to step 9).
8. Turn ignition off. Disconnect PCM harness connector. Using an ohmmeter, check IAT sensor signal circuit for an open. Repair as necessary. Retest system. If wire is okay, go to next step.
9. Check for a poor IAT sensor ground circuit or signal circuit connection at PCM. Repair as necessary. If wires are okay, replace PCM. Retest system.

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation.

If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set. If it is determined that DTC is intermittent, performing DTC P1114 diagnostics may isolate cause of fault.

1. Perform On-Board Diagnostic (OBD) System Check. See «BASIC TESTING»(ref-16258) article. Go to next step.
2. Turn ignition on. Using scan tool, select ENG COOL TEMP. If display is less than 282°F (139°C), go to step 4). If display is not as specified, go to next step.
3. Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0117 is set, check resistance of ECT sensor at specified temperatures. See «ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE»(ref-16268-S04803222662001010800000) . Replace ECT sensor if it does not test as specified. If DTC P0117 is not set, check for an intermittent problem. See «TESTS W/O CODES»(ref-16269) article. ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE Temperature °F (°C) Ohms -40 (-40) 100,700 -22 (-30) 52,700 5 (-15) 21,450 23 (-5) 12,300 41 (5) 7280 59 (15) 4450 77 (25) 2796 95 (35) 1802 113 (45) 1188 140 (60) 667 176 (80) 332 212 (100) 177
4. Turn ignition off. Disconnect ECT sensor harness connector. Turn ignition on. Observe ENG COOL TEMP on scan tool. If display is -38°F (-38°C), replace ECT sensor. Retest system. If display is not as specified, go to next step.
5. Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check ECT sensor signal circuit for short to sensor ground circuit. Repair as necessary. If wire is okay, replace PCM. Retest system.

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation.

If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set. If it is determined that DTC is intermittent, performing DTC P1115 diagnostics may isolate cause of fault.

1. Perform On-Board Diagnostic (OBD) System Check. See «BASIC TESTING»(ref-16258) article. Go to next step.
2. Turn ignition on. Using scan tool, select ENG COOL TEMP. If display is less than -38°F (-39°C), go to step 4). If display is not as specified, go to next step.
3. Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0118 is set, check resistance of ECT sensor at specified temperatures. See ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE table in DTC P0117. Replace ECT sensor if it does not test as specified. If DTC P0118 is not set, check for an intermittent problem, see «DIAGNOSTIC AIDS»(ref-16268-S42346871652001010800000) . See «TESTS W/O CODES»(ref-16269) article.
4. Turn ignition off. Disconnect ECT sensor harness connector. Using a fused jumper wire, connect terminals of ECT sensor harness connector together. Turn ignition on. Observe ENG COOL TEMP value on scan tool. If display is 284°F (140°C), go to step 6). If display is not as specified, go to next step.
5. Jumper ECT sensor signal circuit to ground. If display on scan tool is 284°F ()140°C, go to step 7). If display is not as specified, go to step 8).
6. Check for poor connections at ECT sensor harness connector. Repair as necessary. If connections are okay, replace ECT sensor. Retest system.
7. Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check ECT sensor ground circuit for an open. Repair as necessary. Retest system. If wire is okay, go to step 9).
8. Turn ignition off. Disconnect PCM harness connector. Using an ohmmeter, check ECT sensor signal circuit for an open. Repair as necessary. Retest system. If wire is okay, go to next step.
9. Check for a poor ECT sensor ground circuit or signal circuit connection at PCM. Repair as necessary. If wires are okay, replace PCM. Retest system.

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation.

Low MAP reading can cause PCM incorrect of TP sensor value by PCM. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set. If it is determined that DTC is intermittent, performing DTCs P1121 and DTC P1122 diagnostics may isolate cause of fault.

1. Perform On-Board Diagnostic (OBD) System Check. See «BASIC TESTING»(ref-16258) article. Go to next step.
2. Turn ignition on. Observe MAP sensor parameter on scan tool. If display is less than 65 kPa, go to next step. If display is not as specified, go to step 5).
3. Turn ignition off. Disconnect MAP sensor harness connector. Connect a test light between MAP sensor voltage reference circuit and MAP sensor signal circuit at harness connector. Turn ignition on. If display on scan tool is less than 65 kPa, replace MAP sensor. Retest system. If display is not as specified, go to next step.
4. Turn ignition off. Using an ohmmeter, check for an open, short to ground or short to MAP sensor ground circuit. Repair as necessary. If wire is okay, replace PCM. Retest system.
5. Observe TP sensor angle on scan tool while slowly opening throttle. If display shows a steady increase from zero percent to 100 percent, check for an intermittent problem, see «DIAGNOSTIC AIDS»(ref-16268-S15162662262001010800000) . If display is not as specified, go to next step.
6. Turn ignition off. Disconnect TP sensor harness connector. Turn ignition on. Observe TP sensor parameter on scan tool. If display is zero volts, go to next step. If display is not as specified, go to step 8).
7. Turn ignition off. Connect a test light between voltage reference circuit and sensor signal circuit at TP sensor harness connector. Turn ignition on. If display is 5 volts, replace TP sensor. Retest system. If display is not as specified, go to step 9).
8. Check for the following items: TP sensor signal circuit shorted to power. High resistance in TP sensor ground circuit. Repair as necessary. If no problems are found, replace PCM. Retest system.
9. Check for the following items: Poor connection in TP sensor signal circuit or voltage reference circuit. High resistance in TP sensor voltage reference circuit. Repair as necessary. If no problems are found, replace PCM. Retest system.

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation.

If other DTC(s) are set that share same ground and/or 5-volt reference circuit, check for faulty connections or wiring. The PCM 5-volt reference circuits are internally connected within PCM.

If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set. If it is determined that DTC is intermittent, performing DTC P1122 diagnostics may isolate cause of fault.

1. Perform On-Board Diagnostic (OBD) System Check. See «BASIC TESTING»(ref-16258) article. Go to next step.
2. Turn ignition on. With throttle closed, observe TP sensor parameter on scan tool. If display is less than 0.22 volt, go to step 4). If display is not as specified, go to next step.
3. Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0122 is set, go to next step. If DTC P0122 is not set, check for an intermittent problem, see «DIAGNOSTIC AIDS»(ref-16268-S07856711712001010800000) .
4. Turn ignition off. Disconnect TP sensor harness connector. Using a fused jumper wire, connect voltage reference circuit to sensor signal circuit at harness connector. Turn ignition on. Observe display on scan tool. If display is 5 volts, go to step 10). If display is not as specified, go to next step.
5. Remove jumper wire. Connect a test light between battery positive terminal and sensor signal circuit at TP sensor harness connector. If display on scan tool is 5 volts, go to next step. If display is not as specified, go to step 8).
6. Turn ignition off. Disconnect PCM harness connector. Using an ohmmeter, check for an open or short to ground in voltage reference circuit. Repair as necessary. Retest system. If wire is okay, go to next step.
7. Check voltage reference circuit for poor connection at PCM. Repair as necessary. If connection is okay, replace PCM. Retest system.
8. Turn ignition off. Disconnect PCM harness connector. Using an ohmmeter, check TP sensor signal circuit for an open, short to ground or short to sensor ground circuit. Repair as necessary. Retest system. If wire is okay, go to next step.
9. Check TP sensor signal circuit for poor connection at PCM. Repair as necessary. If connection is okay, replace PCM. Retest system.
10. Check TP sensor signal circuit for poor connection at TP sensor. Repair as necessary. If connection is okay, replace TP sensor. Retest system.

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation.

If other DTC(s) are set that share same ground and/or 5-volt reference circuit, check for faulty connections or wiring. The PCM 5-volt reference circuits are internally connected within PCM.

If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set. If it is determined that DTC is intermittent, performing DTC P1121 diagnostics may isolate cause of fault.

1. Perform On-Board Diagnostic (OBD) System Check. See «BASIC TESTING»(ref-16258) article. Go to next step.
2. Turn ignition on. With throttle closed, observe TP sensor parameter on scan tool. If display is greater than 4.88 volts, go to step 4). If display is not as specified, go to next step.
3. Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0123 is set, go to next step. If DTC P0123 is not set, check for an intermittent problem, see «DIAGNOSTIC AIDS»(ref-16268-S30036743842001010800000) .
4. Turn ignition off. Disconnect TP sensor harness connector. Turn ignition on. Observe display on scan tool. If display is about zero volts, go to next step. If display is not as specified, go to step 6).
5. Using a test light connected to battery positive terminal, probe TP sensor ground circuit at harness connector. If test light comes on, go to step 7). If test light does not come on, go to step 10).
6. Turn ignition off. Disconnect PCM harness connector. Turn ignition on. Using a voltmeter, check TP sensor signal circuit for a short to power. Repair as necessary. If wire is okay, replace PCM. Retest system.
7. Turn ignition on. Observe TP sensor parameter on scan tool while disconnecting each sensor which shares same voltage reference circuit. See «WIRING DIAGRAMS»(ref-16267) article. If display changes while disconnecting a sensor, replace that sensor. Repair as necessary. If display does not change, go to next step.
8. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Using a voltmeter, check voltage reference circuit for short to battery voltage. Repair as necessary. Retest system. If wire is okay, go to next step.
9. Check for poor connection at TP sensor. Repair as necessary. If connection is okay, replace TP sensor. Retest system.
10. Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check for open in TP sensor ground circuit. Repair as necessary. If wire is okay, replace PCM. Retest system.

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform On-Board Diagnostic (OBD) System Check. See «BASIC TESTING»(ref-16258) article. Go to next step.
2. If any Engine Coolant Temperature (ECT) DTCs are set, see appropriate DTC test. If no DTCs are set, go to next step.
3. Allow engine to cool. Ensure coolant level is full. If coolant level is okay, go to next step. If coolant level is low, check cooling system for leaks. Repair as necessary. Retest system.
4. Start engine and let idle. Using scan tool select ENG COOL TEMP. If display increases to greater than 70°F (21°C) within 2 minutes, check for an intermittent problem, see «DIAGNOSTIC AIDS»(ref-16268-S33510138572001010800000) . If display is not as specified, go to next step.
5. Check thermostat for proper operation. Replace thermostat if necessary. Retest system. If thermostat is okay, go to next step.
6. Using a thermometer, check temperature of water in radiator. Compare reading with display on scan tool. If readings are fairly close, check for sticking thermostat or incorrect thermostat application. Repair as necessary. If display readings are not close, go to next step.
7. Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, measure resistance between ECT sensor signal circuit and ECT sensor ground circuit at PCM harness connector. Compare resistance reading with coolant temperature. See «ENGINE COOLANT TEMPERATURE RESISTANCE»(ref-16268-S35976203102001010800000) . If readings are as specified, replace PCM. Retest system. If readings are not as specified, go to next step. ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE Temperature °F (°C) Ohms -40 (-40) 100,700 -22 (-30) 52,700 5 (-15) 21,450 23 (-5) 12,300 41 (5) 7280 59 (15) 4450 77 (25) 2796 95 (35) 1802 113 (45) 1188 140 (60) 667 176 (80) 332 212 (100) 177
8. Using an ohmmeter, check for high resistance in ECT sensor signal circuit or sensor ground circuit. Check for poor connections at PCM and ECT sensor. Repair as necessary. If ECT sensor circuit is okay, replace ECT sensor. Retest system.