P0170

Injector Circuit:

Connector: A-21X, B-01, B-02, B-05, B-06, C-49 <M/T>, C-50 <A/T>:

Fuel Trim Circuit

CIRCUIT OPERATION
- The injector power is supplied from the MFI relay (terminal 1).
- The ECM or PCM controls the injector by turning the power transistor in the ECM or PCM "ON" and "OFF."

TECHNICAL DESCRIPTION
- If a malfunction occurs in the fuel system, the fuel trim value becomes too large or too small.
- The ECM or PCM checks whether the fuel trim value is within a specified range.

DTC SET CONDITIONS

Check Conditions
- During closed loop air/fuel ratio control.
- Intake air temperature is higher than -10°C (14°F).
- Barometric pressure is higher than 76 kPa (11 psi).
- Volume air flow sensor output frequency is 88 Hz or more.

Judgment Criteria
- Long term fuel trim has continued to be higher than +12.5 percent or lower than -12.5 percent for 5 seconds.
- Short term fuel trim has continued to be higher than +10 percent or lower than -10 percent for 5 seconds.

Check Conditions
- During closed loop air/fuel ratio control.
- Intake air temperature is higher than -10°C (14°F).
- Barometric pressure is higher than 76 kPa (11 psi).
- Volume air flow sensor output frequency is 88 Hz or less.

Judgment Criteria
- Long term fuel trim has continued to be higher than +12.5 percent or lower than -12.5 percent for 5 seconds.
- Short term fuel trim has continued to be higher than +15.0 percent or lower than -15.0 percent for 5 seconds.

Check Conditions
- During closed loop air/fuel ratio control.
- Intake air temperature is higher than 10°C (14°F).
- Barometric pressure is higher than 76 kPa (11 psi).
- Volume air flow sensor output frequency is 88 Hz or more.

Judgment Criteria
- Long term fuel trim has continued to be higher than +12.5 percent or lower than -12.5 percent for 5 seconds.
- Short term fuel trim has continued to be higher than +20.0 percent or lower than -10.0 percent for 5 seconds.

Check Conditions
- During closed loop air/fuel ratio control.
- Intake air temperature is higher than -10°C (14°F).
- Barometric pressure is higher then 76 kPa (11 psi).
- Volume air flow sensor output frequency is 88 Hz or more.

Judgment Criteria
- Long term fuel trim has continued to be higher than +12.5 percent or lower than -12.5 percent for 5 seconds.
- Short term fuel trim has continued to be higher than +20.0 percent or lower than -10.0 percent for 5 seconds.

Check Conditions
- During closed loop air/fuel ratio control.
- The heated oxygen sensor (front) is active.

Judgment Criteria
- Long term fuel trim has continued to be higher than +12.5 percent or lower than -12.5 percent for 5 seconds.
- Short term fuel trim has continued to be higher than +25.0 percent or lower than -25.0 percent for 5 seconds.

TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- Volume air flow sensor failed.
- Injector failed.
- Incorrect fuel pressure.
- Air drawn in from gaps in gasket, seals, etc.
- Heated oxygen sensor failed.
- Engine coolant temperature sensor failed.
- Intake air temperature sensor failed.
- Barometric pressure sensor failed.
- Exhaust leak.
- Use of incorrect fuel.
- ECM failed.
- PCM failed.

DIAGNOSIS
Required Special Tool:
MB991502: Scan Tool (MUT-II)

STEP 1. Check the exhaust leaks.
If not malfunctioning, go to Step 2.
If malfunctioning, repair or replace it. Then go to Step 14.

STEP 2. Check the intake system vacuum leak.
If not malfunctioning, go to Step 3.
If malfunctioning, repair or replace it. Then go to Step 14.

CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.

STEP 3. Using scan tool MB991502, check data list item 12: Volume Air Flow Sensor.
1. Connect scan tool MB991502 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991502 to the data reading mode for item 12, Volume Air Flow Sensor.
- When idling, between 25 and 51 Hz (between 2.5 and 5.0 g/s)
- When 2,500 r/min, between 80 and 120 Hz (between 8.5 and 12.7 g/s)

If within specifications, go to Step 4.
If not within specifications, refer to DTC P0100.

- Volume Air Flow Circuit Malfunction.

STEP 4. Using scan tool MB991502, check data list item 13: Intake Air Temperature Sensor.
1. Turn the ignition switch to "ON" position.
2. Set scan tool MB991502 to the data reading mode for item 13, Intake Air Temperature Sensor.
- The intake air Temperature and temperature displayed on the scan tool should approximately match.

If they match, go to Step 5.
If they do not match, refer to DTC P0110 - Intake Air Temperature Circuit Malfunction.

STEP 5. Using scan tool MB991502, check data list item 21: Engine Coolant Temperature Sensor.
1. Turn the ignition switch to "ON" position.
2. Set scan tool MB991502 to the data reading mode for item 21, Engine Coolant Temperature Sensor.
- The engine coolant Temperature and temperature displayed on the scan tool should approximately match.

If they match, go to Step 6.
If they do not match, refer to DTC P0115 - Engine Coolant Temperature Circuit Malfunction.

STEP 6. Using scan tool MB991502, check data list item 25: Barometric Pressure Sensor.
1. Turn the ignition switch to "ON" position.
2. Set scan tool MB991502 to the data reading mode for item 25, Barometric Pressure Sensor.
- At an altitude of 0 m (0 foot), 101 kPa.
- At an altitude of 600 m (1,969 feet), 95 kPa.
- At an altitude of 1,200 m (3,937 feet), 88 kPa.
- At an altitude of 1,800 m (5,906 feet), 81 kPa.

If within specifications, go to Step 7.
If not within specifications, refer to DTC P0105.

- Barometric Pressure Circuit Malfunction.

STEP 7. Check the injectors.
1. Disconnect each injector connector.

2. Measure the resistance between injector side connector 1 and 2 at each injector.

Standard value: 13 - 16 ohms [at 20°C (68°F)]

If within specifications, go to Step 8.
If not within specifications, replace the faulty injector.Then go to Step 14.

STEP 8. Check harness connectors B-01, B-02, B-05, B-06 at the injector for damaged.
If harness connectors B-01, B-02, B-05, B-06 are in good condition, go to Step 9.
If harness connectors B-01, B-02, B-05, B-06 are damaged, repair or replace them.
Refer to Harness Connector Inspection. Then go to Step 14.

STEP 9. Check harness connector C-49 at the ECM or harness connector C-50 at the PCM for damage.
If harness connectors C-49 or C-50 is in good condition, go to Step 10.

If harness connectors C-49 or C-50 is damaged, repair or replace it.
Refer to Harness Connector Inspection. Then go to Step 14.

STEP 10. Check the harness wire between injector connectors B-01, B-02, B-05, B-06 and ECM connector C-49 or PCM connector C-50 .
If the wires between injector connectors B-01, B-02, B-05, B-06 and ECM connector C-49 or PCM connector C-50 are not damaged, go to Step 11.

If the wires between injector connectors B-01, B-02, B-05, B-06 and ECM connector C-49 or PCM connector C-50 are damaged, repair it. Then go to Step 14.

STEP 11. Check the fuel pressure.
Refer to Fuel Pressure Test.
If correct, go to Step 12.

If incorrect, repair or replace it. Then go to Step 14.

STEP 12. Check for entry of foreign matter (water, kerosene, etc) into fuel.
If OK, then go to Step 13.
If contaminated, replace the fuel. Then go to Step 14.

STEP 13. Replace all the injectors.
1. Replace all the injectors.
2. Carry out a test drive with the drive cycle pattern. Refer to Procedure 2 - Fuel Trim Monitor.
3. Check for the diagnostic trouble code (DTC).

If DTC P0170 is not output, the inspection is complete.
If DTC P0170 is output, replace the ECM or PCM. Then go to Step 14.

STEP 14. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Procedure 2 - Fuel Trim Monitor.
2. Read the diagnostic trouble code, and confirm that diagnostic trouble code P0170 does not reset.