Your Vehicle: 2001 Ford Escort ZX2 L4-2.0L DOHC VIN 3
 
Vehicle » Powertrain Management » Computers and Control Systems » Testing and Inspection » Pinpoint Tests » H: Fuel Control - Pinpoint Test » H51 - H111  
 
 
  H51 - H111  
 

H: Fuel Control

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

Continued from: See: H20 - H50

H51 CHECK HO2S SIGNAL AND HO2S GND CIRCUITS FOR OPEN IN HARNESS

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

Is the resistance reading less than 5.0 ohms?
Yes

  • GO to H52

.

No

  • REPAIR open circuit.

H52 CHECK HO2S SIGNAL CIRCUIT FOR SHORT TO GROUND IN HARNESS

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

Is each resistance greater than 10,000 ohms?
Yes

  • GO to H53

.

No

  • REPAIR short circuit.

H53 CHECK HO2S SIGNAL CIRCUIT FOR SHORT TO GROUND

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

Is each resistance greater than 10,000 ohms?
Yes

No

  • REPLACE HO2S.

H54 HO2S CIRCUIT CHECK (FOR RICH DTCS)

  • Disconnect the HO2S related to the DTC received.
  • Key on.
  • Access the correct HO2S PID(s).

Is the reading 0.2 volt or less?
Yes

  • KEY OFF. GO to H56

.

No

  • KEY OFF. GO to H55

.

H55 CHECK HO2S CIRCUIT FOR SHORT TO VPWR AND HO2S HEATER GROUND IN HARNESS

  • Disconnect PCM.
  • Measure resistance between the HO2S SIG and VPWR circuits; and HO2S Signal and HO2S HTR circuits at the PCM harness connector.

Is each resistance greater than 10,000 ohms?
Yes

No

  • REPAIR short circuit.

H56 CHECK HO2S SIGNAL FOR SHORT TO HO2S HEATER CIRCUIT IN THE SENSOR

  • Suspect HO2S sensor disconnected.
  • Measure resistance between the HO2S SIG and HO2S HTR circuits at the HO2S connector.

Is the resistance greater than 10,000 ohms?
Yes

  • KEY OFF. GO to H57

.

No

  • KEY OFF. REPLACE HO2S.

H57 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 HC BEFORE SERVICING.

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

  • KEY OFF.
  • GO to H58

.

No

.

H58 CHECK FUEL SYSTEM FOR PRESSURE STABILITY - FAST LEAKDOWN

  • Cycle key on and off several times.
  • Key on and Engine off, monitor fuel pressure gauge.

Does the fuel pressure remain within 34 kPa (5 psi) of the highest reading after 10 seconds?
Yes

  • GO to H59

.

No

  • Check fuel system for external leaks.

If external leak is detected: GO to HC1 See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 5: Pinpoint Tests\HC: Fuel Delivery System - Pinpoint Test.
If no external leak is detected: GO to H60.

H59 CHECK FUEL SYSTEM FOR PRESSURE STABILITY - SLOW LEAKDOWN

  • Cycle key on then off several times.
  • Key on and engine off, monitor fuel pressure gauge.

Does the fuel pressure remain within 34 kPa (5 psi) of the highest reading after one minute?
Yes

  • For HO2S DTCs displayed with Misfire DTCs:
  • GO to H61

.All other DTCs:

  • GO to H64

.

No

.

H60 CHECK INJECTOR FAULT PIDS AND ASSOCIATED DTCS

  • Access INJ1F-INJ10F PIDs.

Note: If misfire DTCs are present, access only injector fault PIDs corresponding to misfire DTCs.
Is DTC P0201 through P0212 or an injector(s) fault present?
Yes

  • GO to H61

.

No

.

  • For all other DTCs:

GO to H64
.

H61 CHECK FUEL INJECTOR(S) AND HARNESS RESISTANCE

Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.
Note: This erases Continuous Memory DTCs.

  • Disconnected PCM.

Note: Use the injector fault PID to determine the fuel injector circuit(s) requiring testing.

  • Measure resistance between the suspect fuel injector signal circuit and the VPWR circuit at the PCM harness connector.

Is the resistance between 11.0-18.0 ohms?
Yes

No

  • GO to H62

.

H62 CHECK FUEL INJECTOR HARNESS RESISTANCE

  • Disconnect fuel injector harness connector at the suspect fuel injector.
  • Measure resistance of VPWR circuit between PCM harness connector pin and the fuel injector harness connector.
  • Measure resistance of fuel injector circuit between PCM harness connector pin and the fuel injector harness connector.

Is each resistance less than 5.0 ohms?
Yes

  • GO to H63

.

No

  • REPAIR open harness circuit.

H63 CHECK FUEL INJECTOR HARNESS CIRCUIT FOR SHORT TO POWER AND GROUND

  • Disconnect PCM.
  • Suspect fuel injector disconnected.
  • Measure resistance between fuel injector SIG and VPWR circuits; and between fuel injector SIG and PWR GND circuits at the PCM harness connector.

Is each resistance greater than 10,000 ohms?
Yes

  • GO to H64

.

No

  • REPAIR short circuit.

H64 FLOW TEST FUEL INJECTOR(S)

  • Use the Rotunda Injector Tester or equivalent to flow test the fuel injectors according to the instructions for the fuel injector tester.

Is the leakage and flow within specification?
Yes

  • DTC P0171 and P0174:
  • GO to H66

.

.

  • For DTC P1130 and P1150:
  • GO to H66

.

  • For DTC P1131 and P1151:
  • GO to H65

.

  • For DTC P1132 and P1152:
  • GO to H69

.

No

H65 CHECK FOR SECONDARY AIR INTRUSION

Note: If the vehicle is not equipped with Secondary Air Injection System, GO to H66.
An HO2S always lean condition can be caused by:

  • Leak in hoses from secondary air injection pump to engine.
  • Secondary Air diverted upstream of HO2S.
  • Disconnect secondary air injection hose(s) from engine and plug engine side of secondary air injection system.
  • Key on, engine running and at operating temperature.
  • Activate Key On, Engine Running (KOER) Self-Test.

Is DTC P1131 or P1151 present?
Yes

  • GO to H66

.

No

for Secondary Air Injection System diagnostics.

H66 INSPECT INDUCTION SYSTEM FOR AIR LEAKS

  • Inspect the following areas for signs of air leaks:
  • Inlet tube(s) from air cleaner to the throttle body.
  • Gaskets which seal the upper and lower intake manifold.
  • Vacuum hoses and lines for cracks and proper connections.
  • PCV system.

Are there any signs of leaks or damage?
Yes

  • REPAIR as necessary.

No

.

  • DTCs P1131 and P1130 or P1151 and P1150:
  • GO to H67

.

H67 CHECK CYLINDER COMPRESSION

Note: Use the Misfire DTC(s) displayed on prior DTC retrieval to determine which cylinder's compression to check.

  • Check cylinder compression. Refer to Engine.

Are cylinder compression readings within specification?
Yes

  • For DTCs P1131, P1130, P1151 and P1150:
  • GO to H68

.

  • For DTCs P1132 and P1152:
  • GO to H69

.

.

No

  • REPAIR as necessary.

H68 CHECK HO2S'S ABILITY TO GENERATE A VOLTAGE GREATER THAN 0.5 VOLT

Any vacuum or air leaks can cause DTCs P1131, P1130, P1151 and P1150.
Possible causes:

  • Water contamination in connector.
  • Leaking vacuum actuators.
  • Engine sealing (Intake and IAC).
  • EGR system (valve).
  • PCV system (hose and valve).
  • Unmetered air leaks between throttle body and mass air flow (MAF) sensor assembly.
  • Inspect HO2S harness for chafing, burned wires or other damage and repair as necessary.
  • Unplug the suspect HO2S.
  • Connect digital multimeter to the HO2S Signal and HO2S SIG RTN or HO2S GND at the HO2S sensor connector.
  • Run engine at 2000 rpm for three minutes.
  • Rerun KOER Self-Test and monitor HO2S voltage.

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

  • KEY OFF. GO to H71

.

No

  • KEY OFF. REPLACE HO2S.

H69 ATTEMPT TO GENERATE DTC P1131 OR P1151

  • HO2S disconnected.
  • Jumper HO2S Signal at the HO2S harness vehicle connector to the battery negative post.
  • Activate Key On Engine Running (KOER) Self-Test.

Is DTC P1131 or P1151 present?
Yes

  • KEY OFF. REMOVE jumper. GO to H70

.

No

  • KEY OFF. REMOVE jumper. RECONNECT HO2S. DISCONNECT PCM. INSPECT both

ends of connector for damaged or pushed out pins, moisture, corrosion,
loose pins and 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.

H70 HO2S SENSOR VOLTAGE CHECK

  • HO2S disconnected.
  • Connect digital multimeter to HO2S SIG circuit and HO2S SIG RTN 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

  • KEY OFF. RECONNECT vacuum hose and HO2S. GO to H71

.

No

H71 MONITOR HO2S (PID) FOR PROPER SWITCHING WHILE PERFORMING WIGGLE TEST

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

Note: HO2S displayed as O2S on Scan Tool.

  • Monitor suspect HO2S PID.
  • Wiggle, bend and shake small sections of the Electronic Engine Control harness from the PCM to the HO2S.

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

  • KEY OFF. ISOLATE area of harness concern causing lack of HO2S switches and repair.

No

  • KEY OFF. GO to H72

.

H72 TEST DRIVE WHILE MONITORING HO2S PID FOR SWITCHING

Note: This test step requires an observer to monitor HO2S PID.

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

Does the HO2S switch?
Yes

.

No

  • KEY OFF. REPLACE HO2S.

H80 DTC P0136 AND P0156 MONITOR DOWNSTREAM HO2S OUTPUT VOLTAGE FOR ACTIVITY. DTCs P1137, P1138, P1157 AND/OR P1158 INDICATE LACK OF HO2S SWITCHING

Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.
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 P0136, P1137 and P1138=HO2S-12
  • DTC P0156, P1157 and P1158=HO2S-22
  • Visually inspect for:
  • pinched, shorted and corroded wiring and pins
  • crossed sensor wires
  • exhaust leaks
  • contaminated or damaged sensor

Were any concerns found during inspection?
Yes

  • REPAIR as necessary.

No

  • Continuous Memory DTC P0136 and P0156:
  • GO to H81

.

  • All others:
  • GO to H82

.

H81 CHECK FOR KOER DTCS P1137, P1157, P1138 AND P1158

  • Key on.
  • Engine at 2000 rpm for 3 minutes.
  • Activate KOER Self-Test.
  • Check for DTCs.

Is DTC P1137, P1138, P1157 or P1158 present?
Yes

  • KEY OFF. GO to H82

.

No

.

H82 CHECK EXHAUST SYSTEM FOR LEAKS

Note: Any exhaust leaks between the engine and the end of the catalyst can cause DTC P0136 and P0156.

  • Place vehicle on a hoist, transmission in PARK, emergency brake applied, raise vehicle.
  • Inspect the following:
  • Exhaust flanges for leaks.
  • HO2S torque.
  • Check for punctures and cracks in catalyst and pipes leading to them.

Is an exhaust leak present?
Yes

  • REPAIR as necessary.

No

  • GO to H83

.

H83 CHECK HO2S HARNESS CIRCUIT FOR SHORT TO VPWR AND GROUND

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

Is the resistance greater than 10,000 ohms?
Yes

  • GO to H84

.

No

  • REPAIR short in harness.

H84 CHECK HO2S SIGNAL CIRCUIT AND HO2S SIGNAL RETURN CIRCUITS FOR OPEN IN HARNESS

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

Is the resistance reading less than 5.0 ohms?
Yes

  • GO to H85

.

No

  • REPAIR open circuit.

H85 CHECK HO2S CIRCUIT VOLTAGE

  • Connect PCM.
  • Suspect HO2S connected to harness.
  • Key on, engine off.

Note: HO2S displayed as O2S on Scan Tool.

  • Access the correct HO2S PID.

Is the voltage greater than 1.5 volts?
Yes

  • KEY OFF. GO to H88

.

No

  • KEY OFF. GO to H86

.

H86 CHECK HO2S GROUND CIRCUIT IN THE PCM

  • Disconnect PCM.
  • Measure resistance between SIG RTN and PWR GND circuits at the PCM connector.

Is the resistance reading less than 5.0 ohms?
Yes

  • GO to H87

.

No

H87 HO2S CIRCUIT CHECK

  • PCM connected.
  • Suspect HO2S disconnected.
  • Jumper VPWR to HO2S SIG circuit at the HO2S harness connector.
  • Key on.
  • Access HO2S PID.

Is the PID value greater than 1.5 volts?
Yes

  • REPLACE HO2S.

No

H88 CHECK FOR OVER VOLTAGE ON THE HO2S CIRCUIT IN THE PCM

  • Key on.
  • HO2S disconnected.
  • Measure voltage between SIG RTN circuit at the HO2S harness connector and battery negative post.
  • Measure voltage between HO2S SIG circuit at the HO2S harness connector and battery negative post.

Are either voltage readings greater than 1.5 volts?
Yes

No

  • REPLACE HO2S.

H100 KOER DTC P1127

  • Key on, engine on.
  • Access all HO2S heaters and HO2S heater monitor PIDs.

Do all PIDs switch or indicate ON?
Yes

  • Engine still operating. PERFORM KOER Self-Test.

No

  • Operate the engine until all PIDs indicate on. PERFORM KOER Self-Test.

H110 DTCS P1128 AND P1129 KOER

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

  • P1128 refer to the upstream HO2S.
  • P1129 refer to the downstream HO2S.
  • Visually inspect vehicle HO2S harness connector(s) for any indication of being crossed (stretched wires, wire harnesses not mounted properly).

Are there crossed connections or wires?
Yes

  • REPAIR as necessary.

No

  • GO to H111

.

H111 VERIFY PROPER HO2S SIGNAL PIN LOCATION

  • PCM disconnected.
  • Disconnect both of the suspect HO2S sensors from the vehicle harness connector.
  • P1128 = HO2S 11/21 Upstream
  • P1129 = HO2S 12/22 Downstream
  • Measure resistance of HO2S signal circuits between PCM harness connector pins and HO2S harness connector.

Is the resistance less than 5.0 ohms?
Yes

.

No

  • CONNECT HO2S connector to proper HO2S signal pins in the PCM harness connector or HO2S harness connectors. RERUN Quick Test.