HA: Natural Gas Fuel Control

HA: Introduction See: HA: Natural Gas Fuel Control - Introduction

HA30 DTCS P0135, P0141, P0155 AND P0161: HO2S HTR SIGNAL CIRCUIT IS OPEN, SHORTED TO GROUND, SHORTED TO VPWR OR EXCESSIVE CURRENT DRAW

DTC/HO2S Reference List

• DTC P0135 = HO2S HTR-11
• DTC P0141 = HO2S HTR-12
• DTC P0155 = HO2S HTR-21
• 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, contamination, corrosion and proper installation.

Were any concerns found during the visual inspection?
Yes

• REPAIR any concerns found in the visual inspection.

No

• GO to HA31

.

HA31 PERFORM KEY ON ENGINE OFF (KOEO) SELF-TEST

• Key on.
• Engine at 2000 rpm for 1 minute.
• Key off.
• Key on, engine off.
• Perform KOEO Self-Test.

Are DTCs P0135, P0141, P0155 and/or P0161 present?
Yes

• KEY OFF. GO to HA32

.

No

• KEY OFF. 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

.

HA32 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 tested individually.
Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

• 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 HA34

.

No

• KEY OFF. GO to HA33

.

HA33 CHECK VPWR CIRCUIT FOR OPEN IN HARNESS

• Disconnect PCM.
• Measure resistance of VPWR circuit between PCM harness connector pin and HO2S harness connector.

Is the resistance less than 5.0 ohms?
Yes

• GO to HA34

.

No

• CHECK fuse in circuit. If fuse is OK, REPAIR open circuit.

HA34 CHECK HO2S HEATER RESISTANCE

• Measure the resistance of the HO2S HTR.

Is the resistance between 3 and 30 ohms?
Yes

• GO to HA35

.

No

• REPLACE HO2S.

HA35 CHECK HO2S CASE FOR SHORT TO VPWR AND HTR GND

• Measure resistance between the HO2S HTR GND at the HO2S sensor connector and the HO2S sensor case.
• Measure resistance between the HO2S VPWR at the HO2S sensor connector and the HO2S sensor case.

Is the resistance greater than 10,000 ohms?
Yes

• GO to HA36

.

No

• REPLACE HO2S.

HA36 CHECK FOR SHORTS TO OTHER GROUNDS AND VPWR IN THE HO2S HTR GROUND HARNESS CIRCUITS

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

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

Is the resistance greater than 10,000 ohms?
Yes

• GO to HA37

.

No

• REPAIR shorted circuit.

HA37 CHECK HO2S HTR GROUND 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

• 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 or excessive resistance in the heater circuit in

harness.

HA40 DTC P1131, P1151, P1132 AND P1152: UPSTREAM HO2S(S) NOT SWITCHING. DTCs P1130 AND P1150: FUEL SYSTEM NOT SWITCHING AT THE FUEL TRIM (RICH OR LEAN)

HO2S DTCs Reference list

• HO2S-11 = DTCs P1131, P1132 and P1130
• HO2S-21 = DTCs P1151, P1152 and P1150
• Check intake air system for leaks, obstructions, damage and blockage.
• Verify integrity of the PCV system.
• Check for disconnected spark plug wires.
• Check for vacuum leaks.

Are any of the above concerns present?
Yes

• REPAIR as necessary.

No

• GO to DC25 See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 5: Pinpoint Tests\DC: Mass Air Flow (MAF) Sensor - Pinpoint Test

.

HA41 DTCs P0171, P0172, P0174 AND P0175: FUEL SYSTEM AT THE CORRECTED FUEL TRIM

Fuel System DTC Reference list:

• BANK 1 = DTCs P0171 (lean) and P0172 (rich)
• BANK 2 = DTCs P0174 (lean) and P0175 (rich)
• Check intake air system for leaks, obstructions and damage.
• Check air cleaner element, air cleaner housing for blockage.
• Verify fuel level.
• Verify integrity of the PCV system.
• Check for disconnected spark plug wires.
• Check for vacuum leaks.
• Verify customer did not run out of fuel.

Are any of the above concerns present?
Yes

• REPAIR as necessary.

No

• GO to DC25 See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 5: Pinpoint Tests\DC: Mass Air Flow (MAF) Sensor - Pinpoint Test

.

HA42 PERFORM KOER SELF-TEST

• Enter Key On Engine Running (KOER) Self-Test.

Are HO2S DTCs P1131, P1132, P1151 or P1152 present?
Yes

• KEY OFF. GO to HA43

.

No

• KEY OFF. For continuous DTCs P1130, P1150 P0171,

P0174, P0172 and P0175:

• GO to HA43

.

• All others:
• 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

.

HA43 CHECK FUEL PRESSURE

WARNING: THE FUEL SYSTEM IS PRESSURIZED WHEN THE ENGINE IS NOT RUNNING. TO PREVENT INJURY OR FIRE, USE CAUTION WHEN WORKING ON THE FUEL SYSTEM. BECOME FAMILIAR WITH THE WARNING, CAUTION AND NOTE IN PINPOINT TEST HB BEFORE SERVICING.
Note: Fuel rail pressure gauge is part of the NG Special Rotunda Tool Kit 134-00114. Not all Natural Gas vehicles are equipped with a FRP sensor. On vehicles without a FRP sensor, use the values supplied by the fuel rail pressure gauge.

• NG fuel pressure gauge connected at the fuel rail Schrader valve.
• Access FRP PID (if available) and monitor the fuel pressure.
• Key on, engine off. Record pressure readings.
• Key on, engine on. Record pressure readings.
• Increase engine speed to 2500 rpm and maintain for one minute. Record pressure reading.

Are the fuel pressure readings between 552 or 827 kPa (80-120 psi)?
Yes

• KEY OFF. GO to HA44

.

No

• KEY OFF. GO to HB1 See: HB: Natural Gas Fuel Delivery System - Pinpoint Test

.

HA44 CHECK FUEL SYSTEM FOR PRESSURE STABILITY

• Cycle key on and off twice.
• Verify there are no external leaks (service as necessary).

Does the fuel pressure remain within 69 kPa (10 psi) of the highest reading after two minutes?
Yes

• For DTCs P1130, P1150, P0171, P0172, P0174 and

P0175:

• GO to HA45

.

• For No Starts:
• GO to HA45

.

• All other DTCs:
• GO to HA62

.

No

• GO to HB1 See: HB: Natural Gas Fuel Delivery System - Pinpoint Test

.

HA45 CHECK FUEL SYSTEM FOR PRESSURE STABILITY WITH KEY ON

• Access FRP PID, if available, to monitor the fuel pressure. If FRP PID is not available, connect NG Special Rotunda Tool Kit 134-00114, or equivalent to monitor fuel pressure.
• Key On, Engine Off. Monitor the fuel pressure.

Does the fuel pressure remain within 69 kPa (10 psi) of the highest reading after 10 seconds?
Yes

• For No Starts:
• GO to HA46

.

• For DTCs P1130, P1150, P0171 and P0174:
• GO to HA55

.

No

• For DTCs P0172 and P0175:
• GO to HA56

.

HA46 CHECK FUEL INJECTOR(S) ABILITY TO DELIVER FUEL

• Access FRP PID, if available, to monitor the fuel pressure. If FRP PID is not available, connect NG Special Rotunda Tool Kit 134-00114, or equivalent to monitor fuel pressure.
• Cycle key twice.
• Locate and disconnect the inertia fuel shutoff (IFS) switch.
• Crank the engine for ten seconds and monitor the fuel pressure reading.

Was there a pressure drop greater than 34 kPa (20 psi)?
Yes

• The Electronic Engine Control System is not the cause of the

no start. GO to Section 3, Symptom Chart, for further diagnosis. See: Symptom Related Diagnostic Procedures

No

• GO to HA47

.

HA47 CHECK VREF VOLTAGE AT NATURAL GAS (NG) VEHICLE MODULE

• Disconnect PCM.
• NG Module connected.
• Key on, engine off.
• Measure the voltage between VREF and SIG RTN circuits at the NG module harness connector.

Is the voltage reading between 4.0 and 6.0 volts?
Yes

• KEY OFF. For NO START:
• GO to HA48

.

• All others:
• GO to HA57

.

No

• KEY OFF. GO to HA50

.

HA48 CHECK FOR OPEN IN POWER GROUND CIRCUITS

• NG Module disconnected.
• Measure resistance of PWR GND circuit between NG module harness connector pin and battery negative post.

Is the resistance less than 5.0 ohms?
Yes

• GO to HA49

.

No

• REPAIR open circuit.

HA49 CHECK FOR OPEN IN POWER GROUND CIRCUIT IN NG MODULE

• NG Module disconnected.
• Measure the resistance between PWR GND and SIG RTN circuits at the NG Module connector.

Is the resistance less than 5.0 ohms?
Yes

• For NO START:
• GO to HA57

.

• All others:
• RECONNECT PCM, NG Module, and GO to A6 See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 5: Pinpoint Tests\A: No Start - Pinpoint Test

.

No

• REPLACE NG Module.

HA50 IS VREF GREATER THAN 6.0 VOLTS

Is the VREF reading greater than 6.0 volts from the previous test step?
Yes

• GO to HA55

.

No

• GO to HA51

.

HA51 CHECK BATTERY VOLTAGE

• Measure the voltage across the battery terminals.

Is the voltage reading greater than 10.5 volts?
Yes

• GO to HA52

.

No

• REFER to the Charging System-General Information.

HA52 CHECK VPWR AT NG MODULE

• Key on.
• Measure the voltage between VPWR and PWR GND circuits at the NG module harness connector.

Is the voltage reading greater than 10.5 volts?
Yes

• GO to HA54

.

No

• GO to HA53

.

HA53 CHECK VOLTAGE BETWEEN VPWR AT THE NG MODULE AND BATTERY GROUND

• Key on.
• Measure the voltage between VPWR circuit at the NG module harness connector and battery ground.

Is the voltage reading greater than 10.5 volts?
Yes

• REPAIR open ground.

No

• REPAIR open power circuit.

HA54 CHECK VREF VOLTAGE TO THE FUEL TANK PRESSURE SENSOR

• Locate fuel tank pressure sensor at the rear of the vehicle and disconnect (On the Crown Victoria, the fuel tank pressure sensor is located under the vent box cover of the upper tank assembly).
• Key on, engine off.
• Measure voltage between the VREF circuit and SIG RTN circuit at the fuel tank pressure sensor harness connector (refer to schematic at the beginning of this Pinpoint Test for pin location).

Is the voltage reading between 4.0 and 6.0 volts?
Yes

• KEY OFF. REPLACE Fuel Tank Pressure sensor. REFER to Fuel Delivery and Air Induction.

No

• KEY OFF. GO to HA56

.

HA55 CHECK VREF CIRCUIT FOR SHORT TO POWER IN HARNESS

• Fuel tank pressure sensor disconnected.
• Disconnect NG module.
• Key on.
• Measure voltage between the VREF and PWR GND circuits at the NG module harness connector.

Is the voltage reading less than 1.0 volt?
Yes

• REPLACE NG module.

No

• REPAIR short to power.

HA56 CHECK VREF CIRCUIT FOR SHORTED TO PWR GND

Note: Refer to the NG module pin numbers at the beginning of this pinpoint test.

• NG module disconnected.
• Measure resistance between VREF circuit and the SIG RTN, PWR GND and CASE GND circuits at the NG module harness connector.

Is the resistance greater than 10,000 ohms?
Yes

• REPLACE NG module.

No

• REPAIR short to ground.

HA57 CHECK FUEL INJECTOR(S) AND HARNESS RESISTANCE FROM THE NATURAL GAS (NG) MODULE TO THE FUEL INJECTOR(S)

• NG module disconnected.
• Measure resistance between suspect fuel injector circuit Pin(s) and VPWR pins 37/57 at the NG module harness connector (use chart for injector pin location).

• For No Start and DTCs:
• GO to HA60

.

No

• GO to HA58

.

HA58 CHECK FUEL INJECTOR(S) HARNESS RESISTANCE BETWEEN NG MODULE AND FUEL INJECTOR

• Measure resistance of injector circuits between the NG module harness connector Pins and the fuel injector(s) harness connector (use chart from Test StepHA57 for fuel injector pin location).
• Measure resistance between the NG module harness connector VPWR Pins 37/57 and VPWR circuit at the fuel injector harness connector.

Is each resistance less than 5.0 ohms?
Yes

• GO to HA59

.

No

• REPAIR open circuit.

HA59 CHECK FUEL INJECTOR HARNESS CIRCUIT FOR SHORTS TO POWER AND GROUND BETWEEN THE NG MODULE AND INJECTORS

• Measure resistance between the NG module fuel injector Pin(s) and NG module Pins 37/57 and 40/60.

• For DTCs P0172 and P0175, GO to HA61

.

• All Others

:

• REPLACE only damaged fuel injector(s).

No

• REPAIR short circuit.

HA60 CHECK FUEL INJECTOR DRIVER SIGNAL

This test requires a standard 12 volt test lamp.

• NG module connected.

Note: A properly operating system will show a dim glow at idle on the test lamp.

• Connect test lamp between the fuel injector signal circuit pin and VPWR circuit pin at the fuel injector harness connector.
• Crank or start the engine.

Does the test lamp have a dim glow while cranking or running the engine?
Yes

• PCM and NG circuits are OK. For runs rough condition, RETURN

to Section 3, Symptom Charts. See: Symptom Related Diagnostic Procedures

• For No Start condition, GO to A4 See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 5: Pinpoint Tests\A: No Start - Pinpoint Test

.

• All others:
• GO to HA64

.

No

• No light/continuous bright light, GO to HA61

.

HA61 CHECK PCM FUEL INJECTOR HARNESS CIRCUIT RESISTANCE

Note: Refer to the PCM and NG module pin numbers at the beginning of this pinpoint test.

• PCM and NG module disconnected.
• Measure resistance of VPWR circuit between PCM harness connector pins and NG module harness connector pins.
• Measure resistance of the Fuel Injector Pin(s) between the PCM and NG module. (Refer to chart for PCM and NG module pin location.)

• GO to HA62

.

No

• REPAIR open harness circuit.

HA62 CHECK PCM FUEL INJECTOR CIRCUIT FOR SHORT TO POWER AND GROUND IN HARNESS

• Measure resistance between the Fuel Injector circuit pin(s) and VPWR and PWR GND circuits at the PCM harness connector (GO to HA61 and refer to the chart).
• Measure the resistance between the Fuel Injector circuit pin(s) and VPWR, CASE GND and PWR GND circuits at the NG module harness connector (GO to HA61 and refer to the chart).

Is each resistance greater than 10,000 ohms?
Yes

• For DTCs P0172 and P0175:
• GO to HA64

.

• All others:
• GO to HA63

.

No

• REPAIR short circuit.

HA63 CHECK FUEL INJECTOR DRIVER SIGNAL FROM PCM

This test requires a standard 12 volt test lamp.

• PCM connected, NG module disconnected.

Note: A properly operating system will show a dim glow or flicker at idle on the test lamp.

• Connect a test lamp between the VPWR circuit and each from PCM Fuel Injector Signal circuit at the NG module harness connector.
• Crank or start the engine.

Does the test lamp have a dim glow or flicker while cranking or starting the engine?
Yes

• For no starts:
• REPLACE NG module.
• For runs rough:
• Return to symptom chart.
• For DTCs:
• GO to HA64

.

No

• REPLACE PCM.

HA64 FLOW TEST FUEL INJECTOR(S)

Use Rotunda Natural Gas (NG) Injector Tester found in the Special NG Tool Kit 113-00114 or equivalent to flow test NG fuel injectors. Follow the Rotunda Natural Gas (NG) Injector Tester test steps indicated below, or follow the specific instructions included with the injector tester you are using.

• Observe WARNING, CAUTION and NOTE.
• Key off.
• Key on, engine off.
• Note initial FRP sensor pressure using the scan tool.
• Electronic fuel injector tester installed to suspect fuel injector.
• Select pulse width of 200 m sec.
• Activate the fuel injector tester.
• Note final FRP sensor pressure using scan tool.
• Subtract final pressure from initial pressure to find pressure drop.
• Repeat above test procedures for all remaining fuel injectors.

Is the leakage and flow within specification?
Yes

• DTCs P0171, P0172, P0174 and P0175:
• 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

.

• DTCs P1130 and P1150:
• GO to HA66

.

• All others:
• GO to HA65

.

No

• REPLACE fuel injector.

HA65 CHECK CYLINDER COMPRESSION

• Check cylinder compression. Refer to Engine.

Are cylinder compression readings within specification?
Yes

• For DTCs P1131, P1130, P1151 and P1150:
• GO to HA66

.

• For DTCs P1132 and P1152:
• GO to HA71

.

No

• REPAIR as necessary.

HA66 CHECK HO2S INTEGRITY

• Inspect HO2S harness for chafing, burned out wires or other damage and service.
• Inspect HO2S and connector for indications of submersions in water, oil and coolant. Repair as necessary.
• Run engine at 2000 rpm for two minutes.
• Perform Key On Engine Running (KOER) Self-Test.
• Key off.

Are DTCs P1131 and/or P1151 present?
Yes

• GO to HA67

.

No

• 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

.

HA67 CHECK HO2S's ABILITY TO GENERATE A VOLTAGE GREATER THAN 0.5 VOLT

Note: Refer to the PCM pin numbers at the beginning of this pinpoint test.
Any vacuum or air leaks can cause DTCs P1131, P1151, P1130 and P1150.

• Disconnect the suspect HO2S from vehicle harness.
• Connect digital multimeter to the HO2S Signal circuit and HO2S SIG RTN circuit or HO2S GND circuit at the HO2S sensor connector.
• Run engine at 2000 rpm for two minutes.
• Rerun KOER Self-Test and monitor HO2S voltage.

Does voltage reading indicate greater than 0.5 volt during or at the end of Self-Test?
Yes

• GO to HA68

.

No

• REPLACE HO2S.

HA68 CHECK HO2S SIGNAL AND HO2S GROUND CIRCUITS FOR OPEN IN HARNESS

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

Is the resistance reading less than 5.0 ohms?
Yes

• GO to HA69

.

No

• REPAIR open circuit.

HA69 CHECK HO2S CIRCUIT FOR SHORT TO GROUND IN HARNESS

• Measure resistance of HO2S Signal circuit between the PCM harness connector and battery negative post.

Is the resistance greater than 10,000 ohms?
Yes

• GO to HA70

.

No

• REPAIR short circuit.

HA70 CHECK HO2S FOR SHORT TO GROUND

• Measure resistance between HO2S Signal and PWR GND/SIG RTN circuits at the PCM harness connector.

Is the resistance greater than 10,000 ohms?
Yes

• For DTCs P1130 and P1150:
• GO to HA71

.

• For DTCs P1131C and P1151C:
• GO to HA76

.

• For KOER DTCs P1131 and P1151:
• 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

• REPLACE HO2S.

HA71 CHECK FOR DTCS P1132 AND P1152 WITH P1130 AND P1150

• Activate Key On Engine Running (KOER) Self-Test.

Are DTCs P1132 or P1152 present?
Yes

• GO to HA72

.

No

• 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

.

HA72 CHECK HO2S SIGNAL FOR SHORT TO VPWR and VREF

• DTC P1130, P1132=H02S-11
• DTC P1150, P1152=HO2S-21
• Key on, engine off.

Note: HO2S displayed as O2S on Scan Tool.

• Access the HO2S PID for the DTC generated.

Is the voltage greater than 1.0 volt and less than 4.0 volts?
Yes

• GO to HA73

.

No

• GO to HA75

.

HA73 CHECK HO2S CIRCUIT FOR SHORT TO VPWR

• Disconnect sensor.
• Disconnect PCM.

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

• Measure the resistance between the HO2S signal circuit pin(s) and VPWR circuit at the HO2S harness connector.

Is the resistance greater than 10,000 ohms?
Yes

• GO to HA74

.

No

• REPAIR short to power.

HA74 CHECK HO2S SIGNAL FOR SHORT TO HO2S HTR CIRCUIT IN THE SENSOR

• HO2S sensor disconnected.
• Key on, engine off.

Note: HO2S displayed as O2S on Scan Tool.

• Access HO2S PID for DTC(s) received.

Is the HO2S voltage less than 0.2 volt?
Yes

• REPLACE HO2S.

No

• 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).

HA75 ATTEMPT TO GENERATE DTCS P1131 AND P1151

• Disconnect HO2S.
• Connect jumper between HO2S Signal at the HO2S harness connector and battery negative post.
• Activate Key On Engine Running (KOER) Self-Test.

Is DTC P1131 or P1151 present?
Yes

• GO to HA76

.

No

• DISCONNECT PCM. INSPECT both ends of connector for damaged or

pushed out pins, moisture, corrosion, loose pins. REPAIR as necessary. If
OK, 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).

HA76 HO2S SENSOR VOLTAGE CHECK

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

• Disconnect HO2S.
• Connect digital multimeter to HO2S SIG circuit and HO2S SIG RTN circuit at the HO2S sensor connector.
• Disconnect vacuum hose from vacuum tree.
• Start engine and run at 2000 rpm.

Does the voltage reading indicate less than 0.4 volt within 30 seconds?
Yes

• GO to HA77

.

No

• REPLACE HO2S.

HA77 MONITOR HO2S PID FOR PROPER SWITCHING

• Key on, engine running.
• Engine at operating temperature.

Note: HO2S displayed as O2S on Scan Tool.

• Access HO2S PID for DTC received.
• Wiggle, bend and shake small sections of the Electronic Engine Control harness from the PCM to the HO2S harness connector.

Did the HO2S voltage stay high (greater than 0.45 volt) or low (less than 0.45 volt)?
Yes

• ISOLATE cause of lack of HO2S switches and repair.

No

• GO to HA78

.

HA78 TEST DRIVE WHILE MONITORING HO2S PID FOR PROPER SWITCHING

Note: This test step requires an observer to monitor PID for proper operation.

• Access HO2S PID.
• While observer views HO2S PID, test drive vehicle under different road conditions in an attempt to simulate the original fault.

Does HO2S appear to switch properly?
Yes

• UNABLE to duplicate fault. Testing complete at this time.

No

• REPLACE HO2S.

HA90 DTC P1127 KOER

Possible causes:

• Engine not operating long enough prior to performing KOER Self-Test.
• Exhaust system too cool.
• Key on, engine running.
• Access HTR11, 21 PIDs.

Do all PIDs indicate ON?
Yes

• With engine still running, COMPLETE a KOER Self-Test to verify

P1127 is no longer present.

No

• OPERATE engine until all PIDs indicate ON. COMPLETE a KOER Self-Test.

HA100 DTC P1128 KOER

• P1128 refers to the upstream HO2S.

Possible causes:

• Crossed HO2S harness connectors.
• Crossed wiring at HO2S harness connectors.
• Crossed HO2S wiring at PCM 104-pin harness connector.
• Key off.
• Visually inspect HO2S harness connector(s) for any crossed or stretched wires or wire harnesses not mounted properly.

Are there any indications of crossed connectors or wires?
Yes

• REPAIR as necessary.

No

• GO to HA101

.

HA101 VERIFY PROPER HO2S SIGNAL PIN LOCATION

• Disconnect PCM.
• Disconnect both of the suspect HO2S sensors at the HO2S harness connector.
• P1128 = HO2S 11/21 Upstream
• Measure resistance of HO2S SIG circuits between the PCM harness connector and the HO2S harness connectors.
• HO2S-11-Test Pin 60
• HO2S-21-Test Pin 87

Is the resistance less than 5.0 ohms?
Yes

• HO2S SIG circuit is OK.

No

• CONNECT HO2S connector to proper HO2S or RELOCATE HO2S signal

pins in the PCM 104-pin harness connector or HO2S harness connector.