DTC P0172, P0175 [MZI-3.7 (PCM CONNECTOR (2 TYPES))]

DTC P0172 DTC P0175	P0172: System too rich (RH) P0175: System too rich (LH)
DETECTION CONDITION	• P0172 indicates that the fuel/air ratio is too rich (RH). • P0175 indicates that the fuel/air ratio is too rich (LH). • The adaptive fuel strategy continuously monitors the fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit.
POSSIBLE CAUSE	Fuel System: • Damaged or leaking fuel pulse damper • Leaking fuel injectors • Fuel return line restricted • Fuel rail pressure sensor bias • Purge solenoid valve is leaking when the canister is full Base engine: • Engine oil contamination Intake Air System: • Damaged or contaminated MAF sensor

DTC P0172

DTC P0175

P0172: System too rich (RH)

P0175: System too rich (LH)

DETECTION CONDITION

• P0172 indicates that the fuel/air ratio is too rich (RH).

• P0175 indicates that the fuel/air ratio is too rich (LH).

• The adaptive fuel strategy continuously monitors the fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit.

POSSIBLE CAUSE

Fuel System:

• Damaged or leaking fuel pulse damper

• Leaking fuel injectors

• Fuel return line restricted

• Fuel rail pressure sensor bias

• Purge solenoid valve is leaking when the canister is full

Base engine:

• Engine oil contamination

Intake Air System:

• Damaged or contaminated MAF sensor

STEP	INSPECTION	ACTION
1	VERIFY FREEZE FRAME DATA HAS BEEN RECORDED • Has FREEZE FRAME DATA been recorded?	Yes	Go to the next step.
No	Record FREEZE FRAME DATA on the repair order, then go to the next step.
2	VERIFY RELATED SERVICE INFORMATION AVAILABILITY • Verify related Service Information availability. • Is any related Service Information available?	Yes	Perform repair or diagnosis according to the available Service Information. • If the vehicle is not repaired, go to the next step.
No	Go to the next step.
3	VERIFY RELATED PENDING CODE OR STORED DTCS • Turn the ignition switch off then to the ON position (Engine off). • Verify related PENDING CODE or stored DTCs. • Are any DTCs present other than the following: ― P0172, P0175, P2196 or P2198?	Yes	Go to the appropriate DTC troubleshooting procedures. (See DTC TABLE [MZI-3.7 (PCM CONNECTOR (2 TYPES))].)
No	Go to the next step.
4	INSPECT ENTIRE INTAKE AIR SYSTEM FOR DEBRIS, BLOCKAGE OR OTHER DAMAGE • Check the intake air system for obstructions, restrictions, and damage. • Check the throttle plate for obstructions or sludge. • Check the air filter element and housing for blockage. • Is a concern present?	Yes	Repair if necessary. Then go to Step 9.
No	Go to the next step.
5	INSPECT FUEL PRESSURE Warning • Fuel line spills and leakage are dangerous. Fuel can ignite and cause serious injuries or death. Fuel can also irritate skin and eyes. To prevent this, always complete the “BEFORE REPAIR PROCEDURE”. Note • For vehicle specific fuel pressure ranges, refer to the “FUEL LINE PRESSURE INSPECTION”. • Remove the jumper wire(s). • Connect the HO2S connector. • Relieve the fuel pressure. • Connect the mechanical fuel pressure gauge • Pressurize the fuel system. • Turn the ignition switch to the ON position (Engine running) • Allow the fuel pressure to stabilize. • Turn the ignition switch off. • Turn the ignition switch to the ON position (Engine running) • Access the PCM and control the FP PID. • Run the fuel pump to obtain maximum fuel pressure. • Is the fuel pressure within the range for the vehicle being diagnosed?	Yes	Go to the next step.
No	Replace the fuel pump unit. Then go to Step 9.
6	INSPECT FUEL INJECTOR OPERATION • Remove fuel injector. • Inspect the injector operation. • Is the fuel injector normal?	Yes	Go to the next step.
No	Replace the fuel injector. Then go to Step 9.
7	INSPECT HO2S OUTPUT VOLTAGE • Visually inspect the HO2S circuit for exposed wiring, contamination, corrosion and correct assembly. Repair if necessary. • Measure the voltage between HO2S terminal B and D on the component side. • Increase the engine speed to 2,000 rpm for 3 min. • Turn the ignition switch to the ON position (Engine running) • Monitor the signal voltage. • Is the voltage more than 0.5 V at any time during the engine running?	Yes	Go to the next step.
No	Replace the HO2S. Then go to Step 9.
8	PERFORM THOROUGH WIGGLE TEST ON HO2S WIRING HARNESS • Turn the ignition switch off. • Connect the HO2S connector. • Turn the ignition switch to the ON position (Engine running) • Verify that the engine is at normal operating temperature. • Access the PCM and monitor the HO2S signal PID. • Wiggle, shake, and bend small sections of the wiring harness while working from the sensor to the PCM. • While monitoring the HO2S PID, does the HO2S stop switching?	Yes	Isolate the concern and repair if necessary. Then go to the next step.
No	Go to the next step.
9	VERIFY TROUBLESHOOTING OF DTC P0172, P0175 HAS BEEN COMPLETED • Verify that all disconnected connectors are reconnected. • Turn the ignition switch to the ON position (Engine off). • Clear the DTC from the PCM memory using the M-MDS. • Start the engine and run it at idle. • Retrieve DTCs using the M-MDS. • Is the PENDING CODE for this DTC present?	Yes	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION [MZI-3.7].)
No	Go to the next step.
10	VERIFY AFTER REPAIR PROCEDURE • Perform “AFTER REPAIR PROCEDURE”. (See AFTER REPAIR PROCEDURE [MZI-3.7 (PCM CONNECTOR (2 TYPES))].) • Are any DTC present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE [MZI-3.7 (PCM CONNECTOR (2 TYPES))].)
No	Troubleshooting completed.

STEP

INSPECTION

ACTION

VERIFY FREEZE FRAME DATA HAS BEEN RECORDED

• Has FREEZE FRAME DATA been recorded?

Yes

Go to the next step.

Record FREEZE FRAME DATA on the repair order, then go to the next step.

VERIFY RELATED SERVICE INFORMATION AVAILABILITY

• Verify related Service Information availability.

• Is any related Service Information available?

Yes

Perform repair or diagnosis according to the available Service Information.

• If the vehicle is not repaired, go to the next step.

Go to the next step.

VERIFY RELATED PENDING CODE OR STORED DTCS

• Turn the ignition switch off then to the ON position (Engine off).

• Verify related PENDING CODE or stored DTCs.

• Are any DTCs present other than the following:

― P0172, P0175, P2196 or P2198?

Yes

Go to the appropriate DTC troubleshooting procedures.

(See DTC TABLE [MZI-3.7 (PCM CONNECTOR (2 TYPES))].)

Go to the next step.

INSPECT ENTIRE INTAKE AIR SYSTEM FOR DEBRIS, BLOCKAGE OR OTHER DAMAGE

• Check the intake air system for obstructions, restrictions, and damage.

• Check the throttle plate for obstructions or sludge.

• Check the air filter element and housing for blockage.

• Is a concern present?

Yes

Repair if necessary.

Then go to Step 9.

Go to the next step.

INSPECT FUEL PRESSURE

Warning

• Fuel line spills and leakage are dangerous. Fuel can ignite and cause serious injuries or death. Fuel can also irritate skin and eyes. To prevent this, always complete the “BEFORE REPAIR PROCEDURE”.

Note

• For vehicle specific fuel pressure ranges, refer to the “FUEL LINE PRESSURE INSPECTION”.

• Remove the jumper wire(s).

• Connect the HO2S connector.

• Relieve the fuel pressure.

• Connect the mechanical fuel pressure gauge

• Pressurize the fuel system.

• Turn the ignition switch to the ON position (Engine running)

• Allow the fuel pressure to stabilize.

• Turn the ignition switch off.

• Turn the ignition switch to the ON position (Engine running)

• Access the PCM and control the FP PID.

• Run the fuel pump to obtain maximum fuel pressure.

• Is the fuel pressure within the range for the vehicle being diagnosed?

Yes

Go to the next step.

Replace the fuel pump unit.

Then go to Step 9.

INSPECT FUEL INJECTOR OPERATION

• Remove fuel injector.

• Inspect the injector operation.

• Is the fuel injector normal?

Yes

Go to the next step.

Replace the fuel injector.

Then go to Step 9.

INSPECT HO2S OUTPUT VOLTAGE

• Visually inspect the HO2S circuit for exposed wiring, contamination, corrosion and correct assembly. Repair if necessary.

• Measure the voltage between HO2S terminal B and D on the component side.

• Increase the engine speed to 2,000 rpm for 3 min.

• Turn the ignition switch to the ON position (Engine running)

• Monitor the signal voltage.

• Is the voltage more than 0.5 V at any time during the engine running?

Yes

Go to the next step.

Replace the HO2S.

Then go to Step 9.

PERFORM THOROUGH WIGGLE TEST ON HO2S WIRING HARNESS

• Turn the ignition switch off.

• Connect the HO2S connector.

• Turn the ignition switch to the ON position (Engine running)

• Verify that the engine is at normal operating temperature.

• Access the PCM and monitor the HO2S signal PID.

• Wiggle, shake, and bend small sections of the wiring harness while working from the sensor to the PCM.

• While monitoring the HO2S PID, does the HO2S stop switching?

Yes

Isolate the concern and repair if necessary.

Then go to the next step.

Go to the next step.

VERIFY TROUBLESHOOTING OF DTC P0172, P0175 HAS BEEN COMPLETED

• Verify that all disconnected connectors are reconnected.

• Turn the ignition switch to the ON position (Engine off).

• Clear the DTC from the PCM memory using the M-MDS.

• Start the engine and run it at idle.

• Retrieve DTCs using the M-MDS.

• Is the PENDING CODE for this DTC present?

Yes

Replace the PCM, then go to the next step.

(See PCM REMOVAL/INSTALLATION [MZI-3.7].)

Go to the next step.

VERIFY AFTER REPAIR PROCEDURE

• Perform “AFTER REPAIR PROCEDURE”.

(See AFTER REPAIR PROCEDURE [MZI-3.7 (PCM CONNECTOR (2 TYPES))].)

• Are any DTC present?

Yes

Go to the applicable DTC inspection.

(See DTC TABLE [MZI-3.7 (PCM CONNECTOR (2 TYPES))].)

Troubleshooting completed.