P0172

DTC P0172, P0175 FUEL INJECTION SYSTEM FUNCTION

On Board Diagnosis Logic
With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from A/F sensor 1. The ECM calculates the necessary compensation to correct the offset between the actual and the theoretical ratios.
In case the amount of the compensation value is extremely large (the actual mixture ratio is too rich), the ECM judges the condition as the fuel injection system malfunction and illuminates the MIL (2 trip detection logic).

DTC Confirmation Procedure

NOTE:
If DTC Confirmation Procedure has been previously conducted, always perform the following procedure before conducting the next test.
1. Turn ignition switch OFF and wait at least 10 seconds.
2. Turn ignition switch ON.
3. Turn ignition switch OFF and wait at least 10 seconds.

WITH CONSULT-III
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch OFF and wait at least 10 seconds.
3. Turn ignition switch ON.
4. Turn ignition switch OFF and wait at least 10 seconds.
5. Turn ignition switch ON and select "SELF-LEARNING CONT" in "WORK SUPPORT" mode with CONSULT-III.
6. Clear the self-learning control coefficient by touching "CLEAR".
7. Start engine.
If it is difficult to start engine, the fuel injection system has a malfunction.
Performing the following procedure is advised.
a. Crank engine while depressing accelerator pedal.

NOTE:
When depressing accelerator pedal three-fourths (3/4) or more, the control system does not start the engine. Do not depress accelerator pedal too much.
b. If engine starts, go to P0172.
If engine does not start, remove spark plugs and check for fouling, etc.
8. Keep engine at idle for at least 5 minutes.
9. Check 1st trip DTC.
10. The 1st trip DTC P0172 or P0175 should be detected at this stage, if a malfunction exists. If so, go to P0172.

NOTE:
If 1st trip DTC is not detected during above procedure, performing the following procedure is advised.
a. Turn ignition switch OFF and wait at least 10 seconds.
b. Start engine.
c. Maintain the following conditions for at least 10 consecutive minutes.
Hold the accelerator pedal as steady as possible.

d. Check 1st trip DTC.
e. If 1st rip DTC is detected, go to P0172.

WITH GST
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch OFF and wait at least 10 seconds.
3. Turn ignition switch ON.
4. Turn ignition switch OFF and wait at least 10 seconds.

5. Disconnect mass air flow sensor (1) harness connector.
6. Restart engine and let it idle for at least 5 seconds.
7. Stop engine and reconnect mass air flow sensor harness connector.
8. Select Service $03 with GST and check that DTC P0102 is detected.
9. Select Service $04 with GST and erase the DTC P0102.
10. Start engine.
If it is difficult to start engine, the fuel injection system has a malfunction.
Performing the following procedure is advised.
a. Crank engine while depressing accelerator pedal.

NOTE:
When depressing accelerator pedal three-fourths (3/4) or more, the control system does not start the engine. Do not depress accelerator pedal too much.
b. If engine starts, go to P0172.
If engine does not start, remove spark plugs and check for fouling, etc.
11. Keep engine at idle for at least 5 minutes.
12. Check 1st trip DTC.
13. The 1st trip DTC P0172 or P0175 should be detected at this stage, if a malfunction exists. If so, go to P0172.

NOTE:
If 1st trip DTC is not detected during above procedure, performing the following procedure is advised.
a. Turn ignition switch OFF and wait at least 10 seconds.
b. Start engine.
c. Maintain the following conditions for at least 10 consecutive minutes.
Hold the accelerator pedal as steady as possible.

d. Check 1st trip DTC.
e. If 1st rip DTC is detected, go to P0172.

Wiring Diagram

BANK 1

Specification data are reference values and are measured between each terminal and ground.
Pulse signal is measured by CONSULT-III.

CAUTION:
Never use ECM ground terminals when measuring input/output voltage. Doing so may result in damage to the ECM's transistor. Use a ground other than ECM terminals, such as the ground.

BANK 2

Diagnosis Procedure
1.CHECK EXHAUST GAS LEAKAGE
1. Start engine and run it at idle.
2. Listen for an exhaust gas leakage before three way catalyst (manifold).

OK or NG
OK - GO TO 2.
NG - Repair or replace malfunctioning part.
2.CHECK FOR INTAKE AIR LEAKAGE
Listen for an intake air leakage after the mass air flow sensor.
OK or NG
OK - GO TO 3.
NG - Repair or replace malfunctioning part.
3.CHECK AIR FUEL RATIO (A/F) SENSOR 1 INPUT SIGNAL CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect corresponding air fuel ratio (A/F) sensor 1 harness connector.

3. Disconnect ECM harness connector.
4. Check harness continuity between the following terminals. Refer to Wiring Diagram.

Continuity should exist.

5. Check harness continuity between the following terminals and ground. Refer to Wiring Diagram.

Continuity should not exist.

6. Also check harness for short to power.
OK or NG
OK - GO TO 4.
NG - Repair open circuit or short to ground or short to power in harness or connectors.
4.CHECK FUEL PRESSURE
1. Release fuel pressure to zero. Testing and Inspection.
2. Install fuel pressure gauge and check fuel pressure. Testing and Inspection.

At idling: Approximately 350 kPa (3.57 kg/cm2, 51 psi)

OK or NG
OK - GO TO 6.
NG - GO TO 5.
5.DETECT MALFUNCTIONING PART
Check the following.
- Fuel pump and circuit ( Diagnosis Procedure.)
- Fuel pressure regulator ( Testing and Inspection.)
- Repair or replace malfunctioning part.
6.CHECK MASS AIR FLOW SENSOR
With CONSULT-III
1. Install all removed parts.
2. Start engine and warm it up to normal operating temperature.
3. Check "MASS AIR FLOW" in "DATA MONITOR" mode with CONSULT-III.

2.0 - 6.0 gm/sec: at idling
7.0 - 20.0 gm/sec: at 2,500 rpm

With GST
1. Install all removed parts.
2. Start engine and warm it up to normal operating temperature.
3. Check mass air flow sensor signal in Service $01 with GST.

2.0 - 6.0 gm/sec: at idling
7.0 - 20.0 gm/sec: at 2,500 rpm

OK or NG
OK (With CONSULT-III)-GO TO 7.
OK (Without CONSULT-III)-GO TO 8.
NG - Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or grounds. P0101.
7.CHECK FUNCTION OF FUEL INJECTOR
With CONSULT-III
1. Perform "POWER BALANCE" in "ACTIVE TEST" mode with CONSULT-III.
2. Check that each circuit produces a momentary engine speed drop.
OK or NG
OK - GO TO 9.
NG - Perform trouble diagnosis for fuel injector, Diagnosis Procedure.
8.CHECK FUNCTION OF FUEL INJECTOR
Without CONSULT-III

Listen to fuel injector operating sound.

Operating sound should exist.

OK or NG
OK - GO TO 9.
NG - Perform trouble diagnosis for fuel injector, Diagnosis Procedure.
9.CHECK FUEL INJECTOR
1. Remove fuel tube assembly. Component.
Keep fuel hose and all fuel injectors connected to fuel tube.
2. Check that the engine is cooled down and there are no fire hazards near the vehicle.
3. Disconnect all fuel injector harness connectors.
4. Disconnect all ignition coil harness connectors.
5. Prepare pans or saucers under each fuel injector.
6. Crank engine for approximately 3 seconds.
Check that fuel does not drip from fuel injector.
OK or NG
OK (Does not drip.)-GO TO 10.
NG (Drips.)-Replace the fuel injectors from which fuel is dripping. Always replace O-ring with new one.
10.CHECK INTERMITTENT INCIDENT
Diagnosis Procedure.
- INSPECTION END