H: Fuel Control

H: Introduction See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 5: Pinpoint Tests\H: Fuel Control - Introduction

H20 PERFORM KOER SELF-TEST

• Key on, engine running and engine at operating temperature.
• Activate Key On, Engine Running (KOER) Self-Test.

Is DTC P1127, P1128 or P1129 present during KOER Self-Test?
Yes

• GO to Section 4, Powertrain Diagnostic Trouble Code (DTC) Charts See: A L L Diagnostic Trouble Codes ( DTC )\Testing and Inspection\Diagnostic Trouble Code Descriptions and SERVICE DTC P1127, P1128 or P1129.

No

• GO to H21

.

H21 DIAGNOSTIC TROUBLE CODE (DTC) P0133 AND P0153: HO2S RESPONSE TEST

DTC/HO2S Reference List:

• DTC P0133 = HO2S-11
• DTC P0153 = HO2S-21
• Key on, engine off.
• Select Generic OBD II Function from the menu and trigger.
• Press Continue.
• Select Diagnostic Monitoring Test Results from the menu and trigger.
• Scroll to Test ID: 01 trigger and press start.
• Key off. (REFER to Section 2 See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 2: Diagnostic Methods Diagnostic Monitoring Test Results.)

Is the indicated value greater than the minimum threshold?
Yes

• CLEAR the DTCs. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2, Drive Cycles See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 2: Diagnostic Methods\Drive Cycles). GO to H20

0. If test results indicate a pass, testing is complete.

No

• GO to H23

.

H23 CHECK FOR UNMETERED AIR LEAKS

Fuel calculations can be affected by unmetered air leaks.

• Carefully inspect the following areas for potential air leaks:
• Hoses connecting to MAF sensor assembly.
• Hoses connecting to throttle body.
• Intake manifold gasket leaks.
• PCV disconnected.
• Vacuum lines disconnected.
• Improperly seated engine oil dipstick, tube, and oil fill cap.
• Exhaust leaks at flanges and gaskets.

Are any air leaks present?
Yes

• REPAIR source of air leak. CLEAR the DTCs. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2, Drive Cycles See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 2: Diagnostic Methods\Drive Cycles).

No

• GO to H24

.

H24 CHECK HO2S CIRCUIT WIRING

Note: Refer to the PCM connector pin number in the beginning of this pinpoint test.

• Disconnect suspect HO2S.
• Check for water contamination.
• Jumper HO2S signal to VPWR at the HO2S harness connector.
• Key on, engine off.

Note: HO2S displayed as O2S on Scan Tool.

• Access the correct HO2S PID.

Is the voltage greater than 1.50 volts?
Yes

• KEY OFF. REPLACE HO2S. CHANGE oil/filter. CLEAR the DTCs. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2, Drive Cycles See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 2: Diagnostic Methods\Drive Cycles).

No

• KEY OFF. REMOVE jumper wire. GO to H25

.

H25 DTCS P0141 AND P0161: HO2S HEATER CIRCUIT IS OPEN, CHECK HO2S SIGNAL AND SIGNAL RETURN CIRCUITS FOR OPEN IN HARNESS

Note: Refer to the PCM harness connector pin numbers in the beginning of this pinpoint test.
DTC/HO2S Reference List:

• DTC P0141 = HO2S HTR-12
• DTC P0161 = HO2S HTR-22

Note: On some applications, a vehicle hoist is required to access the HO2S harness.

• Visually inspect the HO2S circuit for exposed wiring, water contamination, corrosion and proper assembly.
• Measure resistance of HO2S SIG circuit between PCM harness connector pin and HO2S harness connector.
• Measure resistance of HO2S SIG RTN circuit between PCM harness connector pin and HO2S harness connector.

Is the resistance less than 5.0 ohms?
Yes

• GO to H26

.

No

• REPAIR open circuit. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2, Drive Cycles See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 2: Diagnostic Methods\Drive Cycles).

H26 CHECK HO2S CIRCUIT FOR SHORT TO VPWR IN HARNESS

• Measure resistance between the HO2S SIG and VPWR circuit at the PCM harness connector pin.

Is the resistance greater than 10,000 ohms?
Yes

• GO to H27

.

No

• GO to H28

.

H27 CHECK FOR SOURCE OF POTENTIAL HO2S CONTAMINATION

• Investigate the following items as potential sources of HO2S contamination:
• Use of unapproved silicon sealers.
• Fuel contaminated by silicon additives.
• Excessive oil burning (i.e. rings, valve seals and oil overfill).
• Glycol (antifreeze) leaking internally in the engine.
• Lead contaminated fuel.
• Short drive cycles in cold weather.
• Use of unapproved cleaning agents.

Were any of the above conditions or concerns found during inspection?
Yes

• REPAIR source of contamination. REPLACE HO2S and oil/filter. CLEAR the

DTCs. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2, Drive Cycles See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 2: Diagnostic Methods\Drive Cycles).

No

• If diagnosing DTC P0141 or P0161, GO to H30

0. All others: REPLACE PCM.

H28 VERIFY WIRING IS IN PROPER PIN LOCATION

Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

• Measure resistance of the HO2S SIG circuit and HO2S Signal Return circuit between the PCM harness connector pin and the HO2S harness connector.

Is the resistance less than 5.0 ohms?
Yes

• REPLACE HO2S.

No

• REPAIR as necessary.

H30 DTCS P0135 AND P0155: HO2S HEATER CIRCUIT IS SHORTED TO GROUND, SHORTED TO VPWR OR EXCESSIVE CURRENT DRAW, LOW CURRENT DRAW

Note: Refer to the PCM harness connector pin numbers in the beginning of this pinpoint test.
DTC/HO2S Reference List:

• DTC P0135 = HO2S HTR-11
• DTC P0155 = HO2S HTR-21

Note: On some applications, a vehicle hoist is required to access the HO2S harness.

• Visually inspect the HO2S circuit for exposed wiring, water contamination, corrosion and proper assembly.

Were any concerns found during inspection?
Yes

• REPAIR any concerns found during inspection.

No

• GO to H31

.

H31 PERFORM KEY ON ENGINE OFF (KOEO) SELF-TEST

• Key on, engine off.
• Perform KOEO Self-Test.

Is DTCs P0135, P0141, P0155 or P0161 present?
Yes

• KEY OFF. GO to H32

.

No

• KEY OFF. GO to H33

.

H32 CHECK VPWR VOLTAGE TO HO2S HARNESS CONNECTOR

Note: If DTCs P0135 and P0155 or P0141 and P0161 are displayed, both heater circuits will require testing. DTCs displayed separately are to be tested individually.

• Disconnect the appropriate HO2S(s).
• Key on, engine off.
• Measure voltage between VPWR and SIG RTN circuits at the HO2S harness connector.

Is the voltage greater than 10.5 volts?
Yes

• KEY OFF. GO to H33

.

No

• CHECK fuse in circuit. If fuse is OK, REPAIR open circuit.
• For no VPWR on vehicles equipped with 150 Pin PCM:
• GO to B5 See: B: Electronic Engine Control (EC) Power Relay - Pinpoint Test

.

H33 CHECK HO2S HEATER CIRCUIT FOR SHORT TO VPWR AND GND

• Disconnect PCM.
• Measure resistance between the suspect HO2S HTR circuit and PWR GND circuit.
• Measure resistance between the suspect HO2S HTR circuit and SIG RTN circuit at the HO2S harness connector.
• Measure resistance between the suspect HO2S HTR circuit and VPWR circuit at the HO2S harness connector.

Is each resistance greater than 10,000 ohms?
Yes

• GO to H34

.

No

• REPAIR shorted circuit.

H34 CHECK HO2S HTR CIRCUIT FOR OPEN IN HARNESS

• Measure resistance of the suspect HO2S HTR circuit between PCM harness connector pin and HO2S harness connector.

Is the resistance less than 5.0 ohms?
Yes

• GO to H35

.

No

• REPAIR open or excessive resistance in the heater circuit in harness.

H35 CHECK HO2S HTR RESISTANCE

• Measure the resistance of the HO2S HTR to VPWR (refer to schematic at the beginning of this Pinpoint Test).

Is the resistance between 3 and 30 ohms?
Yes

• GO to H36

.

No

• REPLACE HO2S.

H36 CHECK HO2S CASE FOR SHORT TO VPWR, HTR AND SIG RTN

• Measure resistance between HO2S HTR pin at HO2S connector and the HO2S case.
• Measure resistance between the HO2S HTR pin and the SIG RTN Pin at the HO2S sensor.
• Measure the resistance between the HO2S VPWR pin at the HO2S connector and the HO2S case.

Is the resistance greater than 10,000 ohms?
Yes

• REPLACE PCM.

No

• REPLACE HO2S.

H40 DTCS P0171, P0174, P1130, P1131, P1150, OR P1151: LEAN SYSTEM DTCS

Note: Do not clear the DTCs or reset the keep alive memory (KAM).
Fuel System and HO2S DTC Reference List:

• Bank 1 = DTC P0171 (lean)
• Bank 2 = DTC P0174 (lean)
• HO2S-11 = DTCs P1130 and P1131
• HO2S-21 = DTCs P1150 and P1151
• Access and record the ECT PID from the freeze frame data. The freeze frame data will be used to recreate the concern.
• Retrieve and record the self-test DTCs.

Are any DTCs present other than P0171, P0174, P1130, P1131, P1150, or P1151?
Yes

• DISREGARD the current diagnostic trouble code (DTC) at this time. GO to Section 4, Diagnostic Trouble Code (DTC) Charts See: A L L Diagnostic Trouble Codes ( DTC )\Testing and Inspection\Diagnostic Trouble Code Descriptions and REPAIR the other DTCs.

No

• GO to H41

.

H41 CARRY OUT A VISUAL INSPECTION OF THE INTAKE AIR SYSTEM AND ALL VACUUM HOSES

• Check the intake air system for leaks, obstructions, and damage.
• Inspect the entire length of all the vacuum hoses for:
• proper connections.
• damage or cracks.
• damaged or cracked vacuum tees.
• Verify the integrity of the positive crankcase ventilation (PCV) system.
• Verify the proper PCV valve part number.

Is a concern present?
Yes

• GO to H44

.

No

• GO to H42

.

H42 CHECK FOR THE PRESENCE OF A VACUUM LEAK

Note: Fuel trim values at idle are more sensitive to a vacuum leak. The vacuum leak (unmetered air) represents a larger portion of the total air flow at idle than at part throttle.
Note: The barometric pressure (BARO) PID is not a recommended PID to monitor when diagnosing a vacuum leak. Barometric pressure is calculated during high engine load, when the vacuum leak represents a small portion of the total air flow.
Note: As an example, when calculating the total fuel correction in the following steps, if LONGFT1 = +13% and SHRTFT1 = +23%, the total fuel correction for bank 1 = +36%, also if LONGFT2 = +24% and SHRTFT2 = -3% the total fuel correction for bank 2 = +21%.
Note: If the freeze frame ECT PID is available, stabilize the engine at the temperature recorded by the freeze frame ECT PID. If the freeze frame ECT PID is not available, maintain the engine coolant temperature between 82°C - 101°C (180°F - 215°F) and the intake air temperature less than 46°C (115°F).

• Key on, engine running.
• Access and monitor the ECT or CHT, IAT, LONGFT1, SHRTFT1, LONGFT2 and SHRTFT2 PIDs.
• Allow the engine to stabilize at the temperature necessary to recreate the concern.
• Add and record the LONGFT PID value to the SHRTFT PID value for each bank, for a total fuel correction at idle.
• Increase the engine speed to 2500 rpm for 10 seconds.
• Record the LONGFT1, SHRTFT1, LONGFT2, and SHRTFT2 PID values.
• Add and record the LONGFT PID value to the SHRTFT PID value for each bank, for a total fuel correction at 2500 rpm.

Is the total fuel correction value change, between idle and 2500 rpm, less than 15 percent?
Yes

• No vacuum leak is present.
• GO to H47

.

No

• GO to H43

.

H43 LOCATE THE VACUUM LEAK

• Locate the vacuum tees for the intake air and PCV systems.
• Access and monitor the SHRTFT1 and SHRTFT2 PIDs.
• Restrict the vacuum lines one at a time for 30 seconds. If a vacuum leak is present, the SHRTFT PID values will decrease as the hose is restricted.

Is the decrease in the SHRTFT PIDs greater than 15 percent when one of the vacuum hoses is restricted?
Yes

• GO to H44

.

No

• INSPECT the intake air system for a vacuum leak in the intake manifold or intake gaskets. REPAIR as necessary.
• For repair verification, GO to H44

.

H44 VACUUM LEAK REPAIR VERIFICATION

Note: If the freeze frame ECT PID is available, stabilize the engine at the temperature recorded by the freeze frame ECT PID. If the freeze frame ECT PID is not available, maintain the engine coolant temperature between 82°C - 101°C (180°F - 215°F) and the intake air temperature less than 46°C (115°F).

• Access and monitor the SHRTFT1 and SHRTFT2 PIDs.
• Allow the engine to stabilize at the temperature necessary to recreate the concern.
• Record the SHRTFT1 and SHRTFT2 PID values.
• Key off.
• Repair the vacuum leak.
• Key on, engine running.
• Allow the engine to stabilize at the temperature necessary to recreate the concern.
• Access and monitor the SHRTFT1 and SHRTFT2 PIDs.
• Compare the recorded SHRTFT PID values, prior to the vacuum leak repair, to the current SHRTFT PID values.

Is the decrease in the SHRTFT PIDs greater than 15 percent?
Yes

• Fault found.
• RESET the keep alive memory (KAM). REFER to Section 2, Resetting The Keep Alive Memory (KAM) See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 2: Diagnostic Methods\Resetting The Keep Alive Memory (KAM).

No

• A vacuum leak is still present, GO to H43

.

H45 DTCs P1132 AND P1152: UPSTREAM HO2S NOT SWITCHING.

Note: It is necessary to address all Continuous Memory Ignition and Misfire DTCs, if received during Continuous Memory testing, before addressing any KOER HO2S DTCs.
DTC/HO2S Reference List:

• HO2S-11 = DTC P1132
• HO2S-21 = DTC P1152
• Check intake air system for leaks, obstructions and damage.
• Check air cleaner element, air cleaner housing for blockage.
• Verify integrity of the PCV system.
• Check for vacuum leaks.

Were any concerns found during inspection?
Yes

• REPAIR as necessary.

No

• GO to H47

.

H46 DTCs P0172 AND P0175: FUEL SYSTEM AT THE CORRECTED FUEL TRIM

Note: It is necessary to address all Continuous Memory Ignition and Misfire DTCs, if received during Continuous Memory testing, before addressing any Fuel Trim DTCs.
Fuel System DTC Reference List:

• Bank 1 = DTC P0172 (rich)
• Bank 2 = DTC P0175 (rich)
• Check intake air system for leaks, obstructions and damage.
• Check air cleaner element, air cleaner housing for blockage.
• Verify integrity of the PCV system.
• Check fuel delivery system and filter for restriction.
• Check for vacuum leaks.

Were any concerns found during inspection?
Yes

• REPAIR as necessary. COMPLETE KAM Reset.

No

• GO to H47

.

H47 PERFORM KOER SELF-TEST

• Disconnect fuel vapor hose from intake manifold and plug fitting at intake manifold.
• Start engine and run at 2000 rpm for 5 minutes and return to idle.
• Complete Key On Engine Running (KOER) Self-Test.

Are any HO2S DTCs P1127, P1128, P1129, P1131, P1132, P1151 or P1152 present?
Yes

• KEY OFF. If DTC P1127, P1128 or P1129 is present, GO to Section 4, Powertrain Diagnostic Trouble Code (DTC) Charts See: A L L Diagnostic Trouble Codes ( DTC )\Testing and Inspection\Diagnostic Trouble Code Descriptions and REPAIR those DTCs first.
• DTCs (P1131, P1130) or (P1151, P1150):
• GO to H48

.

• DTCs (P1132, P1130) or (P1152, P1150):
• GO to H54

.

No

• KEY OFF.For Continuous Memory DTCs Only P1130, P1150, P0171, P0174, P0172 and P0175:
• GO to H57

.

• If DTC(s) P1132 and/or P1152 are no longer present, RECONNECT fuel vapor line.
• Vehicles experiencing KOER DTC 1131, 1132, 1151 or 1152:

REFER to Evaporative Emissions System for system leakage.

• All others without recurring DTCs:
• Unable to duplicate or identify fault at this time. GO to Z1 See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 5: Pinpoint Tests\Z: Intermittent - Pinpoint Test

.

H48 HO2S CIRCUIT TEST (WITH LEAN DTCs)

• Disconnect the HO2S related to the DTC.
• Key on, engine off.
• Access the correct HO2S PID.

Note: If arcing occurs (indicating a short), remove jumper and GO to H52 (check fuse in the heater circuit).

• Jumper the HO2S SIG circuit to the VPWR circuit at the HO2S vehicle harness connector.

Is the reading 1.30 volts or greater?
Yes

• KEY OFF. CHECK SIG RTN circuit. GO to H49

.

No

• KEY OFF. GO to H51

.

H49 CHECK SIGNAL RETURN CIRCUIT FOR OPEN

• Measure resistance of HO2S SIG RTN circuit between the HO2S harness connector and the battery negative post.

Is the resistance reading less than 5.0 ohms?
Yes

• GO to H57

.

No

• GO to H50

.

H50 CHECK HO2S SIGNAL RETURN CIRCUIT FOR OPEN IN HARNESS

• Disconnect PCM.
• Measure resistance of HO2S SIG RTN circuit between the PCM harness connector pin and HO2S harness connector.

Is the resistance reading less than 5.0 ohms?
Yes

• REPLACE PCM. REFER to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) See: Programming and Relearning\Flash Electrically Eraseable Programmable Read Only Memory - Flash EEPROM.

No

• REPAIR open circuit.

Continued: See: H51 - H111