Diagnostic Aids

Perform this test when instructed during QUICK TEST or if directed by other test procedure. This test is intended to diagnose the following:

• HO2S and heater.
• HO2S and sensor connection.
• Vacuum systems.
• Fuel injector and/or fuel injector circuitry.
• Powertrain Control Module (PCM).
• Harness circuits: HO2S, HO2SH, INJ 1-6 and VPWR.
  NOTE: HO2S may be displayed on scan tool as O2S.
  NOTE: See TEST DIRECTORY  table for proper starting diagnostic step.

1. 1) DTC P0130: HO2S Circuit Malfunction
   
   DTC P0130 indicates an irrational value in upstream HO2S circuit. Possible causes for fault are as follows:
   • Damaged upstream HO2S or circuit.
   • Intake air system malfunction.
   • Fuel system malfunction.
   • Exhaust system leak.
   • Ignition system malfunction.
   • PCV malfunction.

   Turn ignition off. Connect NGS scan tool to OBD-II DLC. Start engine and run until engine is at normal operating temperature. Access HO2S PIDs. Run engine at different speeds while observing HO2S PID. If HO2S PID is not constantly varying between 0.4-1.0 volt, go to next step. If HO2S PID is 0.4-1.0 volt and constantly varying, turn ignition off. If diagnosing DTCs P0131, P0132, P0133 or P1148, go to step  20). If any other DTC is being diagnosed, go to TEST Z  or see procedures in TROUBLE SHOOTING - NO CODES - VILLAGER article for intermittent diagnostic procedure.

   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 1) to step 11). No test procedures have been omitted.
2. 11) Check HO2S Output Voltage
   
   Warm engine to normal operating temperature. Turn ignition off. Connect NGS scan tool. Access HO2S PIDs. Start engine and observe HO2S PID voltage readings while accelerating engine up to 2000 RPM. If HO2S reaches 0.5 volt or greater, go to step  20). If HO2S never reaches 0.5 volt, go to next step.
3. 12) Check HO2S Circuit Continuity
   
   Turn ignition off. Disconnect suspect HO2S connector. Disconnect PCM connector. Inspect connector for damaged pins and repair if necessary. Measure resistance between suspect HO2S harness connector and appropriate terminal (No. 48 for HO2S11 or No. 54 for HO2S 12). See Fig 1. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open HO2S circuit. Repeat QUICK TEST .
   Fig 1: Identifying HO2S Circuits

   Courtesy of FORD MOTOR CO.
4. 13) Check HO2S Signal Short To Ground
   
   Turn ignition off. Disconnect suspect HO2S sensor. Measure resistance between HO2S11 terminal No. 48 (Light Green wire) and ground, then measure resistance between HO2S12 terminal No. 54 (White wire) and ground. If resistance is less than 10 k/ohms repair short to ground in HO2S circuit. Repeat QUICK TEST . If resistance is greater than 10 k/ohms, go to step  40). If all systems are okay in step  40), go to step  15).
5. 14) Check For Short To Power
   
   Turn ignition off. Disconnect suspect HO2S sensor. Disconnect PCM connector. Measure resistance between PCM connector HO2S11 terminal No. 48 (Light Green wire) or HO2S12 terminal No. 54 (White wire) and KAPWR terminal No. 80 (Yellow wire). See Fig 1. If resistance is less than 10 k/ohms, repair short to power in HO2S circuit. If resistance is greater than 10 k/ohms, go to next step.
6. 15) Erase DTCs
   
   Erase all DTCs. See CLEARING CODES . Run engine at 1500-2000 RPM for at least 3 minutes. Repeat QUICK TEST . If DTC does not return, fault is intermittent. See TEST Z  for intermittent fault diagnosis. If diagnosing DTCs P0131, P0132, P0133, or P1148, go to next step. If diagnosing any other DTC, replace damaged HO2S. If DTC is still present, replace PCM.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 15) to step 20). No test procedures have been omitted.
7. 20) DTC P0135 & P0141: Heater Circuit Malfunction
   
   DTC P0135 indicates a malfunction in upstream oxygen sensor heater circuit. DTC P0141 indicates a malfunction in downstream oxygen sensor heater circuit. Possible causes for malfunction are as follows:
   • Faulty or damaged HO2S.
   • Poor harness connection.
   • Open or short in heater circuit.
   • Open heater GND circuit.
   • Faulty PCM.

   Examine HO2S harness connectors for damage or corrosion. Repair connectors as necessary. If HO2S harness connectors are okay, go to next step.

8. 21) Check HO2S Heater PID
   
   Turn ignition off. Connect NGS scan tool to fuse panel DLC. Access appropriate HTR PID. Start and run engine at idle, then increase engine speed to more than 4200 RPM while observing PID data. HTR PID should be OFF for 5 seconds (heater OFF) after engine starts, then stay ON (heater ON) at idle. Raise engine speed above 4200 RPM. HTR PID should turn OFF (heater OFF) above 4200 RPM, then turn ON (heater ON) below 4200 RPM. If HTR PID stays off for 5 seconds after engine start, then stays ON at idle and turns OFF above 4200 RPM, go to step  24). If HTR PID indicates ON at all times, go to step  23). If HTR PID indicates OFF at all times, go to step  24).
   NOTE: Following test may set unrelated DTCs. Clear all DTCs after this test step.
9. 22) Check Appropriate Heater Circuit
   
   Disconnect HO2S11 or HO2S12 harness connectors. Measure voltage between HTR11 (Black wire) or HTR12 (Yellow wire) and ground circuits at HO2S11/HO2S12 harness connector. Start engine and monitor heater voltage. Voltage will be high (battery voltage) with heater off and low (less than one volt) with heater on. Heater voltage should be high for 5 seconds (heater off) after engine start, then stay low (heater on) at idle. Increase engine speed above 4200 RPM. Heater voltage should be high (heater off) above 4200 RPM, then stay low (heater on) below 4200 RPM. If heater voltage stays high for 5 seconds after engine start, becomes low at idle and changes to high above 4200 RPM, go to step  24). If voltage stays low, go to next step. If voltage stays high, go to step  24).
10. 23) Check HO2SH Circuit For Short To Ground
    
    Turn ignition off. Disconnect suspect HO2S sensor. Disconnect PCM connector. Measure resistance between PCM connector HTR11 (Black wire) or HTR12 (Yellow wire) circuits and ground. If resistance is greater than 10 k/ohms, go to next step. If resistance is less than 10 k/ohms, repair short to ground in sensor heater circuit. Repeat QUICK TEST .
11. 24) Check VPWR Circuit Continuity
    
    Turn ignition off. Disconnect suspect HO2S sensor. Turn ignition on. Measure voltage of VPWR circuit (Blue/Yellow wire) between HO2S harness connector and ground. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, repair open VPWR circuit. Restore all electrical connections and repeat QUICK TEST .
12. 25) Check HO2S Heater Circuit Continuity
    
    Turn ignition off. Disconnect suspect HO2S sensor. Measure resistance of appropriate HTR circuit between HO2S harness connector and PCM harness connector. See CIRCUIT PIN IDENTIFICATION  table. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open HO2SH circuit. Restore electrical connections. Repeat QUICK TEST .
13. 26) Check HO2S Heater
    
    Turn ignition off. Disconnect suspect HO2S sensor. Measure resistance between Blue/Yellow wire and Black wire terminals (on sensor). If resistance is not approximately 6 ohms, replace HO2S. Restore electrical connections and repeat QUICK TEST . If resistance is approximately 6 ohms, replace PCM. Restore electrical connections and repeat QUICK TEST.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 26) to step 40). No test procedures have been omitted.
14. 40) DTC P0171 & P0172: Fuel Trim Malfunction
    
    DTC P0171 indicates air/fuel ratio too lean. DTC P0172 indicates air/fuel ratio too rich. Possible causes for malfunction are as follows:
    • Excessive fuel pressure.
    • Leaking fuel injector(s).
    • Leaking fuel pressure regulator.
    • Low fuel pressure.
    • Restricted fuel injectors.
    • Faulty HO2S or circuit.
    • Induction system air leaks.
    • Restricted air filter.
    • Faulty PCV system.
    • Engine mechanical problem.
    • Oil level over full.
    • Ignition system malfunction.

    If any of the listed areas are faulty, repair as necessary. If all of the listed areas are okay, go to next step.

15. 41) Fuel Delivery System
    
    Connect fuel pressure gauge to fuel rail or fuel filter. Start engine and observe fuel pressure. If fuel pressure is 34-43 psi (234-294 kPa), go to next step. If fuel pressure is not as specified, go to TEST HC .
    NOTE: Before performing following test, determine whether misfire DTCs are displayed with fuel control DTCs. Use misfire DTCs to determine injector circuits requiring testing.
16. 42) Check Injector Harness & Resistance
    
    Disconnect PCM. Measure resistance of suspect injector between injector and PCM KAPWR circuit terminal No. 80 (Yellow wire) at PCM harness connector. See CIRCUIT PIN IDENTIFICATION  table. If resistance is 10-14 ohms, injector and harness resistance are okay. Go to step  45). If resistance is not 1-14 ohms, go to next step.
17. 43) Check Injector Circuit Continuity
    
    Turn ignition off. Disconnect injector harness connector. Measure resistance of Yellow wire circuit between injector harness KAPWR circuit and PCM connector terminal No. 80. Also measure resistance between injector signal circuit between injector connector and PCM harness connector. See Fig 2. Also see CIRCUIT PIN IDENTIFICATION  table. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit.
    Fig 2: Identifying Fuel Injector Circuits & Connector Terminals

    Courtesy of FORD MOTOR CO.
18. 44) Check Injector Harness Circuit For Short To Power Or Ground
    
    Turn ignition off. Disconnect PCM. Disconnect suspect injector harness connector. Measure resistance between PCM harness connector injector signal and KAPWR, ground, and SIG RTN (Black/Yellow wire) circuits. See CIRCUIT PIN IDENTIFICATION  table. Also measure resistance between injector signal circuit at PCM harness connector and chassis ground. If each resistance measurement is greater than 10 k/ohms, go to next step. If each resistance measurement is 10 k/ohms or less, repair short circuit in wiring. Restore electrical connections and repeat QUICK TEST .
19. 45) Check Injector Driver
    
    Ensure PCM is connected. Connect a standard non-powered test light between KAPWR (Yellow wire) circuit and injector signal circuit at each injector harness connector. See CIRCUIT PIN IDENTIFICATION  table. Crank engine. If test light dimly glows while cranking, go to next step. If test light does not glow or glows brightly, replace PCM. Restore electrical connections and repeat QUICK TEST .
20. 46) Check Injector Flow
    
    Using Rotunda Fuel Injector Tester Cleaner (164-R3759), check flow rate of each injector. Replace any injectors that are not within leakage and flow specification. If all injectors are within leakage and flow specification, fault is intermittent. See TEST Z .