NO.14 POOR FUEL ECONOMY [WL-C, WE-C]

14	POOR FUEL ECONOMY
DESCRIPTION	• Fuel economy is unsatisfactory.
POSSIBLE CAUSE	• Incorrect idle speed • A/C system improper operation • Intake -air system clogging or restriction • Engine cooling system malfunction • Poor fuel quality • Improper coolant level • Erratic signal from CKP sensor • Erratic signal from CMP sensor • Fuel pressure sensor or related circuit malfunction • ECT sensor or related circuit malfunction • Boost sensor or related circuit malfunction • Accelerator pedal position (APP) sensor or related circuit malfunction • MAF sensor/IAT sensor No.2 or related circuit malfunction • IAT sensor No.1 or related circuit malfunction • VSS or related circuit malfunction • Turbocharger malfunction • Charge air cooler malfunction • Low engine compression • Improper valve timing • Exhaust system and/or oxidation catalytic converter clogging • Incorrect fuel injection timing • Fuel injector malfunction • Supply pump malfunction • Fuel leakage • Fuel line clogging or restriction • Fuel filter clogging or restriction • Fuel inlet‐filter clogging or restriction • Brake dragging • EGR system malfunction • Vacuum leakage • Clutch slippage • Variable boost control (VBC) system malfunction • Coolant heater system malfunction Warning The following troubleshooting flow chart contains the fuel system diagnosis and repair procedures. Read the following warnings before performing the fuel system services: • Fuel vapor is hazardous. It can easily ignite, causing serious injury and damage. Always keep sparks and flames away from fuel. • Fuel line spills and leakage are dangerous. Fuel can ignite and cause serious injury or death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete “BEFORE REPAIR PROCEDURE” and “AFTER REPAIR PROCEDURE” described in this manual.

POOR FUEL ECONOMY

DESCRIPTION

• Fuel economy is unsatisfactory.

POSSIBLE CAUSE

• Incorrect idle speed

• A/C system improper operation

• Intake -air system clogging or restriction

• Engine cooling system malfunction

• Poor fuel quality

• Improper coolant level

• Erratic signal from CKP sensor

• Erratic signal from CMP sensor

• Fuel pressure sensor or related circuit malfunction

• ECT sensor or related circuit malfunction

• Boost sensor or related circuit malfunction

• Accelerator pedal position (APP) sensor or related circuit malfunction

• MAF sensor/IAT sensor No.2 or related circuit malfunction

• IAT sensor No.1 or related circuit malfunction

• VSS or related circuit malfunction

• Turbocharger malfunction

• Charge air cooler malfunction

• Low engine compression

• Improper valve timing

• Exhaust system and/or oxidation catalytic converter clogging

• Incorrect fuel injection timing

• Fuel injector malfunction

• Supply pump malfunction

• Fuel leakage

• Fuel line clogging or restriction

• Fuel filter clogging or restriction

• Fuel inlet‐filter clogging or restriction

• Brake dragging

• EGR system malfunction

• Vacuum leakage

• Clutch slippage

• Variable boost control (VBC) system malfunction

• Coolant heater system malfunction

Warning

The following troubleshooting flow chart contains the fuel system diagnosis and repair procedures. Read the following warnings before performing the fuel system services:

• Fuel vapor is hazardous. It can easily ignite, causing serious injury and damage. Always keep sparks and flames away from fuel.

• Fuel line spills and leakage are dangerous. Fuel can ignite and cause serious injury or death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete “BEFORE REPAIR PROCEDURE” and “AFTER REPAIR PROCEDURE” described in this manual.

STEP	INSPECTION	RESULTS	ACTION
1	Inspect the following: • Fuel quality (e.g.: including water contamination, winter/summer blend) • Fuel line/fuel filter clogging and/or restriction • Fuel inlet‐filter clogging and/or restriction • Fuel line leakage • Intake-air system restriction • Exhaust system and/or oxidation catalytic converter restriction • Charge air cooler condition (restriction or damaged) • Vacuum leakage Are all items normal?	Yes	Go to the next step.
No	Service if necessary. Repeat Step 1.
2	Is the brake system functioning properly?	Yes	Go to the next step.
No	Inspect for cause.
3	Perform the self-test function using the M-MDS. Turn the engine switch to the ON position (Engine off). Retrieve any DTCs. Are any DTCs displayed?	Yes	DTC is displayed: Go to the appropriate DTC test. (See DTC TABLE [WL-C, WE-C (Thailand, General (L.H.D. R.H.D.) specs.)].) Communication error message is displayed: Inspect the following: • Open circuit between main relay and PCM terminal 201, 203, 205 • Open circuit main relay and PCM terminal 219 • Main relay stuck open • Open or poor ground circuit (PCM terminal 202, 204, 206) • Poor connection to vehicle body ground
No	No DTC is displayed: Go to the next step.
4	Note • The following test should be performed on the vehicles with an A/C system. If the following test cannot be performed due to engine stalling, go to the next step. • Go to the next step for vehicles without n A/C system Connect the pressure gauge to the A/C line. Turn the blower and A/C switches on. Is the pressure within the specifications?	Yes	Go to the next step.
No	A/C is always on: Go to the symptom troubleshooting “NO.24 A/C ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY [WL-C, WE-C]”. Other symptoms: Inspect the following: • Refrigerant charging amount • Cooling fan operation
5	Access the ECT PID. Drive the vehicle while monitoring the PID. Is the PID within the specification?	Yes	Go to the next step.
No	Inspect for coolant leakage, cooling fan operation or thermostat operation.
6	Inspect the idle speed. (See ENGINE TUNE-UP [WL-C, WE-C].) Is the idle speed normal?	Yes	Go to the next step.
No	Go to symptom troubleshooting “NO.7 SLOW RETURN TO IDLE [WL-C, WE-C]”.
7	Perform the EGR system inspection. Is the EGR system normal?	Yes	Go to the next step.
No	Repair or replace the malfunctioning part according to the EGR system operation results.
8	Inspect the APP sensor. (See ACCELERATOR PEDAL POSITION (APP) SENSOR INSPECTION [WL-C, WE-C].) Is the APP sensor normal?	Yes	Go to the next step.
No	Replace the accelerator pedal component.
9	Is the engine compression correct? (See COMPRESSION INSPECTION [WL-C, WE-C].)	Yes	Go to the next step.
No	Inspect the following: • Damaged valve seat • Worn valve stem and valve guide • Worn or stuck piston ring • Worn piston, piston ring or cylinder • Improper valve timing Service if necessary.
10	Inspect the fuel injector. (See FUEL INJECTOR INSPECTION [WL-C, WE-C].) Is the fuel injector normal?	Yes	Go to the next step.
No	Repair or replace if necessary. (See FUEL INJECTOR REMOVAL/INSTALLATION [WL-C, WE-C].)
11	Perform the turbocharger inspection. (See TURBOCHARGER INSPECTION [WL-C, WE-C].) Is the turbocharger normal?	Yes	Go to the next step.
No	Replace the turbocharger.
12	Inspect the guide blade valve operation. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [WL-C, WE-C].) Is the there any malfunction?	Yes	Repair or replace if necessary.
No	Go to the next step.
13	Inspect the CKP sensor. (See CRANKSHAFT POSITION (CKP) SENSOR INSPECTION [WL-C, WE-C].) (See CRANKSHAFT POSITION (CKP) SENSOR REMOVAL/INSTALLATION [WL-C, WE-C].) Is the CKP sensor normal?	Yes	Go to the next step.
No	Replace the CKP sensor. Then go to the next step.
14	Visually inspect the CMP sensor and the teeth of the pulse wheel. Are the CMP sensor and the teeth of the pulse wheel normal?	Yes	Inspect the following PIDs: (See PCM INSPECTION (Thailand, General (L.H.D. R.H.D.) specs.) [WL-C, WE-C].) • ECT • IAT • MAF • MAP • RPM • VSS If the PID value is not as specified, repair or replace malfunctioning parts. If the PID value is normal, go to the next step.
No	Replace malfunctioning parts.
15	Inspect the timing belt for the following: • Chipping of gear teeth • Low tension • Breakage damage or cracks Is the timing belt normal?	Yes	Inspect the following: • Clutch slippage • CKP sensor • Boost sensor and related circuit • Brake system for dragging • Coolant heater system • Glow system If normal, remove and inspect supply pump.
No	If the timing is incorrect, adjust the valve timing. If the timing belt is not normal, replace the timing belt.
16	Verify test results. • If normal, return to the diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX [WL-C, WE-C].) • If the malfunction remains, inspect the related Service Information and perform repair or diagnosis. ― If the vehicle is repaired, troubleshooting completed. ― If the vehicle is not repaired or additional diagnostic information is not available, reprogram the PCM if later calibration is available. Retest.

STEP

INSPECTION

RESULTS

ACTION

Inspect the following:

• Fuel quality (e.g.: including water contamination, winter/summer blend)

• Fuel line/fuel filter clogging and/or restriction

• Fuel inlet‐filter clogging and/or restriction

• Fuel line leakage

• Intake-air system restriction

• Exhaust system and/or oxidation catalytic converter restriction

• Charge air cooler condition (restriction or damaged)

• Vacuum leakage

Are all items normal?

Yes

Go to the next step.

Service if necessary.

Repeat Step 1.

Is the brake system functioning properly?

Yes

Go to the next step.

Inspect for cause.

Perform the self-test function using the M-MDS.

Turn the engine switch to the ON position (Engine off).

Retrieve any DTCs.

Are any DTCs displayed?

Yes

DTC is displayed:

Go to the appropriate DTC test.

(See DTC TABLE [WL-C, WE-C (Thailand, General (L.H.D. R.H.D.) specs.)].)

Communication error message is displayed:

Inspect the following:

• Open circuit between main relay and PCM terminal 201, 203, 205

• Open circuit main relay and PCM terminal 219

• Main relay stuck open

• Open or poor ground circuit (PCM terminal 202, 204, 206)

• Poor connection to vehicle body ground

No DTC is displayed:

Go to the next step.

Note

• The following test should be performed on the vehicles with an A/C system. If the following test cannot be performed due to engine stalling, go to the next step.

• Go to the next step for vehicles without n A/C system

Connect the pressure gauge to the A/C line.

Turn the blower and A/C switches on.

Is the pressure within the specifications?

Yes

Go to the next step.

A/C is always on:

Go to the symptom troubleshooting “NO.24 A/C ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY [WL-C, WE-C]”.

Other symptoms:

Inspect the following:

• Refrigerant charging amount

• Cooling fan operation

Access the ECT PID.

Drive the vehicle while monitoring the PID.

Is the PID within the specification?

Yes

Go to the next step.

Inspect for coolant leakage, cooling fan operation or thermostat operation.

Inspect the idle speed.

(See ENGINE TUNE-UP [WL-C, WE-C].)

Is the idle speed normal?

Yes

Go to the next step.

Go to symptom troubleshooting “NO.7 SLOW RETURN TO IDLE [WL-C, WE-C]”.

Perform the EGR system inspection.

Is the EGR system normal?

Yes

Go to the next step.

Repair or replace the malfunctioning part according to the EGR system operation results.

Inspect the APP sensor.

(See ACCELERATOR PEDAL POSITION (APP) SENSOR INSPECTION [WL-C, WE-C].)

Is the APP sensor normal?

Yes

Go to the next step.

Replace the accelerator pedal component.

Is the engine compression correct?

(See COMPRESSION INSPECTION [WL-C, WE-C].)

Yes

Go to the next step.

Inspect the following:

• Damaged valve seat

• Worn valve stem and valve guide

• Worn or stuck piston ring

• Worn piston, piston ring or cylinder

• Improper valve timing

Service if necessary.

Inspect the fuel injector.

(See FUEL INJECTOR INSPECTION [WL-C, WE-C].)

Is the fuel injector normal?

Yes

Go to the next step.

Repair or replace if necessary.

(See FUEL INJECTOR REMOVAL/INSTALLATION [WL-C, WE-C].)

Perform the turbocharger inspection.

(See TURBOCHARGER INSPECTION [WL-C, WE-C].)

Is the turbocharger normal?

Yes

Go to the next step.

Replace the turbocharger.

Inspect the guide blade valve operation.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [WL-C, WE-C].)

Is the there any malfunction?

Yes

Repair or replace if necessary.

Go to the next step.

Inspect the CKP sensor.

(See CRANKSHAFT POSITION (CKP) SENSOR INSPECTION [WL-C, WE-C].)

(See CRANKSHAFT POSITION (CKP) SENSOR REMOVAL/INSTALLATION [WL-C, WE-C].)

Is the CKP sensor normal?

Yes

Go to the next step.

Replace the CKP sensor.

Then go to the next step.

Visually inspect the CMP sensor and the teeth of the pulse wheel.

Are the CMP sensor and the teeth of the pulse wheel normal?

Yes

Inspect the following PIDs:

(See PCM INSPECTION (Thailand, General (L.H.D. R.H.D.) specs.) [WL-C, WE-C].)

• ECT

• IAT

• MAF

• MAP

• RPM

• VSS

If the PID value is not as specified, repair or replace malfunctioning parts.

If the PID value is normal, go to the next step.

Replace malfunctioning parts.

Inspect the timing belt for the following:

• Chipping of gear teeth

• Low tension

• Breakage damage or cracks

Is the timing belt normal?

Yes

Inspect the following:

• Clutch slippage

• CKP sensor

• Boost sensor and related circuit

• Brake system for dragging

• Coolant heater system

• Glow system

If normal, remove and inspect supply pump.

If the timing is incorrect, adjust the valve timing.

If the timing belt is not normal, replace the timing belt.

Verify test results.

• If normal, return to the diagnostic index to service any additional symptoms.

(See SYMPTOM DIAGNOSTIC INDEX [WL-C, WE-C].)

• If the malfunction remains, inspect the related Service Information and perform repair or diagnosis.

― If the vehicle is repaired, troubleshooting completed.

― If the vehicle is not repaired or additional diagnostic information is not available, reprogram the PCM if later calibration is available. Retest.