Engine Controls - Self-Diagnostics - Except 2.0L Turbo: Other

Malfunction Indicator Light

Malfunction Indicator Light (MIL) may also be referred to as Service Engine Soon light. If all systems are normal, immediately after the ignition switch is turned to ON position, MIL will illuminate for 5 seconds, then go out. When ECM/PCM determines an emissions related malfunction exists, ECM/PCM will turn the MIL on. If ECM/PCM determines that the malfunction no longer exists, it will turn the MIL off.

If MIL will not come on for bulb check or MIL stays on with no Diagnostic Trouble Codes (DTCs) present, diagnose MIL circuit malfunction. See MALFUNCTION INDICATOR LIGHT .

Freeze Frame Data

The conditions at the time a malfunction is detected will be stored in ECM/PCM as freeze frame data. While multiple DTCs may be recorded, only one freeze frame is recorded. DTCs are assigned a priority with fuel and misfire codes having the highest priority. Non-emissions related DTCs have the lowest priority. The DTC with the highest priority will be the one recorded in freeze frame. Freeze frame records are cleared when DTCs are erased. Freeze frame data recorded are

Engine Coolant Temperature.
Engine RPM.
Vehicle Speed.
Long Term Fuel Trim (Displayed As Percent).
Short Term Fuel Trim (Displayed As Percent).
Fuel Control Condition (Open Or Closed Loop).
Calculated Load Value (Displayed As Percent).
DTC During Data Recording.

OBD-II Drive Cycles

Manufacturer defines drive cycle as a pattern of driving that meets code set criteria for ECM/PCM to monitor a particular system/component. Drive cycle is used to verify repair by reproducing conditions during which fault occurred. There are 6 different drive cycles. These are: Catalytic Converter Monitor, EVAP System Leak Monitor, Heated Oxygen Sensor (HO2S) Monitor, EGR Monitor, Fuel Trim Monitor and Other Monitor. For the requirements to run a drive cycle, see appropriate drive cycle in OBD-II DRIVE CYCLES under VERIFYING REPAIRS. DO NOT run drive cycle if outside air temperature is less than 14°F (-10°C).

Failure Management

When main sensor malfunctions are detected, ECM/PCM will enter fail-safe mode. Default values will be substituted in ECM/PCM calculations for faulty sensor as follows

Volume Airflow Sensor - ECM/PCM will use engine speed (crankshaft position sensor) and Throttle Position (TP) sensor signals to determine injector drive time and basic ignition timing. Idle Air Control (IAC) motor remains in a fixed position.
Intake Air Temperature (IAT) Sensor Sets at a default of 77°F (25°C).
Throttle Position (TP) Sensor Fuel injection amount will not increase during acceleration due to unreliable TP sensor signal.
Engine Coolant Temperature (ECT) Sensor Sets at a default of 176°F (80°C).
Camshaft Position (CMP) Sensor ECM/PCM will command injectors to inject fuel into cylinders in normal 1-3-4-2 order, but may not be synchronized with camshaft timing.
Barometric Pressure (BARO) Sensor Sets at a default of 30 in. Hg (101 kPa).
Knock Sensor Switches ignition timing from high octane to fixed at low octane.
Heated Oxygen Sensor (HO2S) Front Closed-loop fuel control is not allowed.
Heated Oxygen Sensor (HO2S) Rear Allows closed-loop fuel control using front HO2S signals.
Generator FR Terminal Generator output suppression control of electrical load is not performed.
Communication Line With Transaxle Control Module (TCM) Ignition timing retard control is inoperative when transaxle speeds change.
Misfire Detection Fuel supply is stopped to cylinder if misfiring will damage catalytic converter.

SERVICE PRECAUTIONS

Before proceeding with diagnosis, following precautions must be observed

Ensure vehicle has a fully charged battery and functional charging system. Codes cannot be retrieved if battery voltage is too low.
Visually inspect connectors and circuit wiring being worked on.
DO NOT disconnect battery or ECM/PCM. This will erase any DTCs stored in ECM/PCM.
DO NOT cause short circuits when performing electrical tests. This will set additional DTCs, making diagnosis of original problem more difficult.
DO NOT use a test light in place of a DVOM. Use DVOM with 10-megohm impedance.
When checking for spark, ensure coil wire is NOT more than 1/4" from chassis ground. If coil wire is more than 1/4" from chassis ground, damage to vehicle electronics and/or ECM/PCM may result.
DO NOT prolong testing of fuel injectors. Engine may hydrostatically (liquid) lock.

Hard Failures

Hard failures will cause Malfunction Indicator Light (MIL) to illuminate and remain on until problem is repaired. If MIL comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using diagnostic (code) charts. If a sensor fails, PCM will use a substitute value in its calculations to continue engine operation. In this condition, commonly known as limp-in mode, vehicle will run, but driveability will not be optimum.

VERIFYING REPAIRS

Note. Erasing/clearing DTCs will also erase freeze frame data and reset readiness test status.

Procedure for verifying repairs depends on scan tool functions and whether DTC is set by one-trip or two-trip fault detection logic. The two-trip fault detection logic requires fault to be detected on 2 consecutive drive cycles, with each meeting the code set criteria, before DTC will set and MIL will illuminate. DTCs using the one-trip fault detection logic will set the first time fault is detected. If fault is emissions related, PCM will also turn on MIL. Most DTCs use two-trip; fault detection logic. To determine which logic is used to set DTC, see DIAGNOSTIC TROUBLE CODE DEFINITIONS , then go to appropriate repair verification procedure.

VERIFYING REPAIRS FOR ONE-TRIP DTCS

Note freeze frame data. Clear DTCs. Drive vehicle in manner approximating conditions recorded in freeze frame in order to verify repair. Using scan tool, check for DTCs.

VERIFYING REPAIRS FOR TWO-TRIP DTCS

For catalytic converter, Heated Oxygen Sensor (HO2S), EGR, fuel trim and Evaporative Emissions (EVAP) system related DTCs, it will be necessary to drive vehicle according to drive cycle that allows ECM/PCM to monitor the fault. Clear DTCs and drive vehicle according to appropriate monitor. See appropriate monitor under OBD-II DRIVE CYCLES .

If drive cycle used to verify repair runs catalytic converter monitor, HO2S monitor, EGR monitor, fuel trim monitor or EVAP system leak monitor, repair may be verified in one drive cycle by checking readiness test status. Readiness test status is an indicator showing whether monitor has run or not run. If ECM/PCM ran monitor and found no faults, readiness test status will display COMPLETE or READY. Repair is verified.

If ECM/PCM found fault during drive cycle or monitor did not meet criteria to run, readiness test status will display INCOMPLETE or NOT READY. Perform drive cycle again. The second time drive cycle is run, readiness test status will display COMPLETE or READY whether or not a fault was found. It will be necessary to check for DTCs. If readiness test status does not display COMPLETE or READY after 2 drive cycles, one or both drive cycles failed to meet criteria necessary for ECM/PCM to run monitor.

For systems and components monitored by other monitor, record freeze frame data. Clear DTCs. Drive vehicle in manner approximating conditions recorded in freeze frame in order to verify repair.

Other monitor does not have readiness test status because other monitor runs continuously. Manufacturer's MUT-II Scan Tool (MB991502) provides mode 2 (increased sensitivity) and mode 5 (provisional DTCs) functions which allow repairs to be verified after one drive cycle. Generic scan tools may or may not have these functions. If scan tool does not have these functions, drive vehicle under conditions approximating freeze frame data twice, then check for DTCs.

MUT-II scan tool mode 2 (increased sensitivity) allows single drive cycle testing of emissions related DTCs. Mode 2 commands ECM/PCM to illuminate MIL and set DTC on first occurrence of fault when code set criteria are being met. If MIL does not illuminate during drive cycle, repair is verified. Return to mode 1 (normal) by turning ignition off or reselecting mode 1. When scan tool returns to mode 1, freeze frame data, readiness test status and DTCs are erased.

MUT-II scan tool mode 5 (provisional DTCs) can be used to verify repairs after only one drive cycle by reporting fault as provisional (pending) DTC. Mode 5 is limited to reporting faults related to misfire, fuel system and faults detected by other monitor.

EVAP System Leak Monitor

This monitor applies to DTCs P0441, P0442, P0451, P0452, P0455 and P0456. Following conditions must be met during the test

Engine coolant temperature must be 113°F (45°C) or less with engine off before test drive is started.
Atmospheric temperature is 41-113°F (5-45°C).
Selector lever is in "D" range (A/T).
Test may not run if fuel tank is over 2/3 full.

Monitor takes about 8 minutes to complete. To run monitor, use illustration. (Scheme 31) Perform steps as follows

Remove all test equipment from vehicle and install all components and connectors that were removed or disconnected during testing.
Start engine.
Accelerate vehicle to 55-60 MPH.
Travel for 200 seconds or more while keeping speed at 55-60 MPH. Use 5th gear on M/T.
While keeping accelerator pedal position constant, keep vehicle speed at 55-60 MPH for 150 seconds or more (this is when monitor runs).
Return vehicle to shop and turn ignition off.
Recheck for DTC(s). If any DTC(s) is set, diagnose affected DTC(s). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152075-S09950415582003011300000) .

Scheme 31

Fuel Trim Monitor

This monitor applies to DTCs P0171 and P0172. Following conditions must be met during the test

Engine coolant temperature is 176-207°F (80-97°C).
Atmospheric temperature is 14-140°F (-10°C to 60°C).
Selector lever is in "D" range (A/T).

Monitor takes about 35 minutes to complete. To run monitor, use illustration. (Scheme 32) Perform steps as follows

Remove all test equipment from vehicle and install all components and connectors that were removed or disconnected during testing.
Warm engine to normal operating temperature. Turn ignition off.
Start engine and accelerate vehicle to 55-60 MPH. Use 5th gear on M/T.
Drive at 55-60 MPH for 30 minutes or more. During this period DO NOT drive at constant speed for more than 120 seconds. Carry out gradual deceleration and acceleration within every 120 second time frame. Depressing brake pedal is okay, but avoid abrupt braking.
Return vehicle to shop and turn ignition off. Recheck for DTC(s). If any DTC(s) is set, diagnose affected DTC(s). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152075-S09950415582003011300000) .

Scheme 32

Catalytic Converter Monitor

This monitor applies to DTC P0421. Following conditions must be met during the test

Atmospheric temperature is 14°F (-10°C) or more.
A/C switch is off.
Selector lever is in "D" range (A/T).

Monitor takes about 20 minutes to complete. To run monitor, use illustration. (Scheme 33) Perform steps as follows

Remove all test equipment from vehicle and install all components and connectors that were removed or disconnected during testing.
Start engine.
Accelerate vehicle to 45 MPH.
Travel 300 seconds or more while keeping speed at 45-60 MPH. Use 5th gear on M/T.
Decelerate to 35-40 MPH.
While keeping accelerator pedal opening degree constant (use 4th gear on M/T), keep speed at 35-40 MPH for 90 seconds or more.
Fully close throttle and decelerate for 10 seconds. Then, quickly accelerate until speed is 35-40 MPH. Then repeat steps 5 and 6 five more times.
Return vehicle to shop. Turn engine off. Recheck for DTC(s). If any DTC(s) is set, diagnose affected DTC(s). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152075-S09950415582003011300000) .

Scheme 33

Heated Oxygen Sensor Monitor

This monitor applies to DTCs P0133 and P0139. Following conditions must be met during the test

Engine coolant temperature must be 176°F (80°C) or more.
Atmospheric temperature is 14°F (-10°C) or more.
Selector lever is in "D" range (A/T).

Monitor takes about 5 minutes to complete. To run monitor, use illustration. (Scheme 34) Perform steps as follows

Remove all test equipment from vehicle and install all components and connectors that were removed or disconnected during testing.
After engine is completely warmed up, turn ignition off.
Start engine and quickly accelerate vehicle to 35-40 MPH.
While keeping accelerator pedal position constant (use 4th gear on M/T), keep speed at 35-40 MPH for 120 seconds or more.
Return vehicle to shop and turn ignition off. Recheck for DTC(s). If any DTC(s) is set, diagnose affected DTC(s). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152075-S09950415582003011300000) .

Scheme 34

EGR Monitor

This monitor applies to DTC P0401. Following conditions must be met during the test

Engine coolant temperature must be 176°F (80°C) or more.
Atmospheric temperature is 41°F (5°C) or more.
Selector lever is in "D" range (A/T).
A/C switch is off.

Monitor takes about 10 minutes to complete. To run monitor, use illustration. (Scheme 35) Perform steps as follows

Remove all test equipment from vehicle and install all components and connectors that were removed or disconnected during testing.
After engine is completely warmed up, turn ignition off.
Start engine and quickly accelerate vehicle to 35-40 MPH.
Keep speed constant at 35-40 MPH for 20 seconds or more. Use 4th gear on M/T.
Decelerate by closing throttle fully and allowing engine speed to drop from 2000-3000 RPM to about 900 RPM. DO NOT apply brakes. DO NOT turn steering wheel or operate light switch during this time.
Accelerate to 35-40 MPH, then hold speed constant for 20 seconds or more. Repeat steps 4 and 5 seven more times.
Return vehicle to shop and turn ignition off. Recheck for DTC(s). If any DTC(s) is set, diagnose affected DTC(s). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152075-S09950415582003011300000) .

Scheme 35

Other Monitor

This monitor applies to DTCs not covered by the rest of the monitors. Following conditions must be met during the test

Engine coolant temperature must be 176°F (80°C) or more.
Atmospheric temperature is 41°F (5°C) or more.
Selector lever is in "D" range (A/T).

Monitor takes about 10 minutes to complete. To run monitor, use illustration. (Scheme 36) Perform steps as follows

Remove all test equipment from vehicle and install all components and connectors that were removed or disconnected during testing.
After engine is completely warmed up, turn ignition off.
Start engine and quickly accelerate vehicle to 35-40 MPH and travel for 300 seconds or more. Use 4th gear on M/T.
Return vehicle to shop and let idle. While engine is idling, A/C switch must be in OFF position, lights and accessories must be off, steering wheel must be in straight-ahead position, and transmission in Neutral. After idling for 5 minutes, turn ignition off.
Recheck for DTC(s). If any DTC(s) is set, diagnose affected DTC(s). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152075-S09950415582003011300000) .

Scheme 36

SUMMARY

If no there are no DTCs or provisional codes, and driveability symptoms exist, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures. See INTERMITTENT DIAGNOSTIC TROUBLE CODES .

No Communication With All Systems

Turn ignition off. Check voltage between ground and OBD-II Data Link Connector (OBD-II DLC) terminal No. 16 (Green/Red wire). see scheme 7and (Scheme 42). If battery voltage is present, go to next step. If battery voltage is not present, repair connectors and/or wiring between OBD-II DLC and power supply.
Check for continuity between ground and OBD-II DLC terminals No. 4 (Black wire) and No. 5 (Black wire). If continuity exists at each terminal, repair or replace scan tool as necessary. If continuity does not exist at either terminal, repair wiring between ground and OBD-II DLC.

No Communication With ECM Or PCM

Turn ignition off. Check ECM (M/T) or PCM (A/T) harness connectors for loose, damaged or corroded terminals. ECM or PCM is located behind glove compartment. (Scheme 43) Repair as necessary. If problem does not exist, go to next step.
Using a DVOM, check for open or short to ground in OBD-II DLC terminal No. 7 (Orange wire) and ECM harness connector C-117 terminal No. 62 (M/T) or PCM harness connector C-116 terminal No. 85 (A/T). see scheme 8and (Scheme 42). Repair circuit as necessary. If problem does not exist, go to next step.
Remove MFI relay from underhood fuse/relay block (located near air cleaner box). Check MFI relay connector for loose, damaged or corroded terminals. Repair or replace as necessary. If problem does not exist, go to next step.
Check MFI relay. See FUEL PUMP RELAY & MFI RELAY under RELAYS under MOTORS, RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING article. If problem exists, replace MFI relay. If problem does not exist, reinstall MFI relay and go to next step.
Turn ignition on, with engine off. Measure voltage between ground and MFI relay connector terminals No. 1 (Black/Yellow wire) and No. 2 (Black/Yellow wire). If battery voltage is present at both terminals, go to next step. If battery voltage is not present at either or both terminals, repair Black/Yellow wire between underhood fuse/relay block and power supply.
Turn ignition off. Disconnect ECM or PCM harness connectors. Check connector terminals. Repair or replace as necessary. If problem does not exist, go to next step.
Turn ignition on, with engine off. Check voltage between ground and ECM harness connector C-115 terminal No. 82 (M/T) or PCM harness connector C-116 terminal No. 98 (A/T). Battery voltage should be present. If battery voltage is present, go to next step. If battery voltage is not present, repair Black/Red wire between ECM or PCM harness connector and ignition switch.
Check voltage between ground and ECM harness connector C-115 terminal No. 80 (M/T) or PCM harness connector C-118 terminal No. 66 (A/T). If battery voltage is present, go to next step. If battery voltage is not present, repair Red/Black wire between ECM or PCM and power supply.
Turn ignition off. Disconnect ECM harness connector C-121 (M/T) or PCM harness connector C118 (A/T). Check resistance between ECM harness connector C-121 terminals No. 13 and No. 26 (M/T) or PCM harness connector C-118 terminals No. 42 and No. 48 (A/T). If resistance is less than 2 ohms, go to next step. If resistance is not less than 2 ohms, repair open in circuit.
Check voltage between ground and ECM harness connector C-119 terminal No. 38 (M/T) or PCM harness connector C-118 terminal No. 49 (A/T). If battery voltage is present, go to next step. If battery voltage is not present, repair open in circuit to power supply.
Connect a jumper wire between ECM harness connector C-119 terminal No. 38 (M/T) or PCM harness connector C-118 terminal No. 49 (A/T). Turn ignition on, with engine off. Using DVOM, check voltage between ECM harness connector C-118 terminals No. 41 and No. 47 (A/T) or PCM harness connector C-121 terminals No. 12 and No. 25. If battery voltage is present, replace ECM or PCM. If battery voltage is not present, check harness connectors for damage. Repair or replace as necessary. If harness connectors are okay, check for open in circuit to MFI relay.

Scheme 37

Scheme 37: MALFUNCTION INDICATOR LIGHT

Scheme 38

Malfunction Indicator Light (MIL) Does Not Illuminate

Turn ignition on, with engine off. Using scan tool, check data list item No. 16: POWER SUPPLY VOLTAGE. If battery voltage is present, go to step 11. If battery voltage is not present, go to next step.
Turn ignition off. Remove MFI relay from underhood fuse/relay block (located near air cleaner box). Check MFI relay connector for loose, damaged or corroded terminals. Repair as necessary. If relay connector is okay, go to next step.
Check MFI relay. See «FUEL PUMP RELAY & MFI RELAY»(ref-152080-S13017408082003011300000) under RELAYS under MOTORS, RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING article. If problem exists, replace MFI relay. If relay is okay, go to next step.
Remove MFI relay from underhood fuse/relay block. Turn ignition on, with engine off. Using a DVOM, measure voltage between ground and MFI relay connector terminals No. 1 (Black/Yellow wire) and No. 2 (Black/Yellow wire). (Scheme 38) If battery voltage is present at both terminals, go to next step. If battery voltage is not present at either or both terminals, repair Black/Yellow wire between underhood fuse/relay block and power supply.
Turn ignition off. Disconnect ECM harness connector C-119 (M/T) or PCM harness connector C-120 (A/T). Check connector terminals for damage. Repair or replace as necessary. If connector terminals are okay, go to next step.
Turn ignition on, with engine off. Check voltage between ground and ECM harness connector C-119 terminal No. 36 (M/T) or PCM harness connector C-120 terminal No. 98 (A/T). (Scheme 37) If battery voltage is present, go to next step. If battery voltage is not present, repair Black/Red wire between ECM or PCM harness connector and ignition switch.
Check voltage between ground and ECM harness connector C-115 terminal No. 80 (M/T) or PCM harness connector C-118 terminal No. 66 (A/T). (Scheme 38) If battery voltage is present, go to next step. If battery voltage is not present, repair Red/Black wire between ECM or PCM and power supply.
Turn ignition off. Check resistance between ground ECM harness connector C-121 terminals No. 13 and No. 26 (M/T) or PCM harness connector C-118 terminals No. 42 and No. 48 (A/T). If resistance on each terminal is less than 2 ohms, go to next step. If resistance on each terminal is not less than 2 ohms, repair open in circuit.
Check voltage between ground and ECM harness connector C-119 terminal No. 38 (M/T) or PCM harness connector C-118 terminal No. 49 (A/T). If battery voltage is present, go to next step. If battery voltage is not present, repair open in circuit to power supply.
Connect a jumper wire between ground and ECM harness connector C-119 terminal No. 38 (M/T) or PCM harness connector C-118 terminal No. 49 (A/T). Turn ignition on, with engine off. Using DVOM, check voltage between ECM harness connector C-118 terminals No. 41 and No. 47 (A/T) or PCM harness connector C-121 terminals No. 12 and No. 25. If battery voltage is present, replace ECM or PCM. If battery voltage is not present, check harness connectors for damage. Repair or replace as necessary. If harness connectors are okay, check for open in circuit to MFI relay. Repair as necessary.
Turn ignition off. Check for burned out MIL bulb. If bulb is burned out, replace bulb. If bulb is okay, go to next step.
Disconnect combination meter (instrument cluster) 20-pin harness connector C-01. Check combination meter connectors for loose, damaged or corroded terminals. Repair or replace as necessary. If connector terminals are okay, go to next step.
Turn ignition on, with engine off. Using a DVOM, check voltage between ground and combination meter harness connector C-01 terminal No. 9 (Yellow/Red wire). If battery voltage is present, go to next step. If battery voltage is not present, repair circuit between combination meter and ignition switch.
Turn ignition off. Reconnect combination meter harness connector. Disconnect ECM harness connector C-119 (M/T) or PCM harness connector C-120 (A/T). Check connector for loose, damaged or corroded terminals. Repair or replace as necessary. If connector terminals are okay, go to next step.
Turn ignition on. Using DVOM, check voltage between ground and ECM harness connector C-119 terminal No. 36 (M/T) or PCM harness connector C-120 terminal No. 22 (A/T). If battery voltage is present, replace ECM or PCM. If battery voltage is not present, check ECM or PCM harness connectors for damage. Repair or replace as necessary. If harness connectors are okay, repair open in circuit between combination meter harness connector and ECM or PCM harness connector.

Malfunction Indicator Light (MIL) Stays On

Turn ignition on, with engine off. Using scan tool, check for stored DTCs. See «ENTERING ON-BOARD DIAGNOSTICS»(ref-152075-S15602899592003011300000) under SELF-DIAGNOSTIC SYSTEM. If DTCs are present, record all DTCs and go to appropriate test(s) under «DIAGNOSTIC TESTS»(ref-152075-S03262998472003011300000). If no DTCs are present, go to next step.
Turn ignition off. Disconnect 21-pin combination meter (instrument cluster) harness connector C-01. Using a DVOM, check for continuity between ground and combination meter harness connector C-01 terminal No. 17 (White/Blue wire). (Scheme 37) If continuity exists, repair short to ground in White/Blue wire between combination meter and ECM or PCM. If continuity does not exist, replace ECM or PCM.