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 02S.

Fig 1: Identifying Fuel Injector Circuits & Connector Terminals

Fig 2: Identifying HO2S Circuits

CIRCUIT PIN IDENTIFICATION

Circuit	Breakout Box Pin No.	PCM Pin No.	Wire Color
HO2S11	26	46	Lt. Green
HO2SH11	83	85	Black
HO2S12	78	52	White
HO2SH12	84	86	Yellow
INJ1	69	72	Green/Orange
INJ2	74	77	Green
INJ3	71	74	Green/Red
INJ4	76	79	Yellow/Purple
INJ5	79	81	Yellow/Green
INJ6	82	84	Gray/Blue
KAPWR	67	70	Yellow

TEST DIRECTORY

DTC	Action
P0130 & P0136	Go To Step 1)
P0135 & P0141	Go To Step 20)
P0171 & P0172	Go To Step 40)

NOTE: DTC P0130 indicates upstream HO2S fault. DTC P0136 indicates downstream HO2S fault.

1) DTC P0130: HO2S Circuit Malfunction

DTCs 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 step 11). If HO2S PID is 0.4-1.0 volt and constantly varying, HO2S is okay at this time. Go to CIRCUIT TEST Z or TESTS W/O CODES 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.

11) Check HO2S Output Voltage

Warm engine to normal operating temperature. Turn ignition off. Connect NGS scan tool to OBD-II DLC. Access HO2S PIDs. Start engine and run at 2000 RPM while observing HO2S PID. If HO2S reaches 0.6 volt or greater, go to step 14). If HO2S never reaches 0.6 volt, go to next step.

12) Check HO2S Circuit Continuity

Turn ignition off. Disconnect suspect HO2S connector. Disconnect PCM connector. Inspect connector for damaged pins and repair if necessary. Install breakout box (leave PCM disconnected). Measure resistance between suspect HO2S harness connector and appropriate breakout box test pin (No. 26 for HO2S11 or 78 for HO2S 12). 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 .

13) Check HO2S Signal Short To Ground

Turn ignition off. Disconnect suspect HO2S sensor. Install breakout box (leave PCM disconnected). Measure resistance between breakout box test pin No. 26, 78 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, perform step 40). If all systems are okay in step 40), go to step 15).

14) Check For Short To Power

Turn ignition off. Disconnect suspect HO2S sensor. Install breakout box (leave PCM disconnected). Turn ignition on. Measure resistance between breakout box test pin No. 26 or 78 and pin No. 67 (VPWR). 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.

15) Erase DTCs

Erase DTCs from memory. See CLEARING CODES (WITHOUT SCAN TOOL) or CLEARING CODES (WITH SCAN TOOL) . Run engine at 1500-2000 RPM for at least 3 minutes. Repeat QUICK TEST . If DTC P0130 or P0136 returns, replace HO2S in question. If DTC P0130 does not return, fault is intermittent. See CIRCUIT TEST Z for intermittent fault diagnosis.
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.

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 etc. Repair connectors as necessary. If HO2S harness connectors are okay, go to next step.

21) Check HO2S Heater PID

Turn ignition off. Connect NGS scan tool to OBD-II DLC. Access appropriate HTR PID. Start engine and run at idle, then increase engine speed to more than 4200 RPM while observing PID data. PID should indicate ON at idle and OFF at more than 4200 RPM. If HO2SH PID indicates as specified, go to next step. If HO2SH PID does not indicate ON at all, go to step 23). If PID indicates OFF at all times, go to step 24).

22) Check Appropriate Heater Circuit

Turn ignition off. Install breakout box (connect PCM). Measure voltage between breakout box test pin No. 83 or 84 and test pin No. 10 (GND). Start engine and monitor heater voltage. Voltage will be high with heater off and low with heater on. Heater voltage should be low at idle and 4200 RPM. If voltage is as specified, go to step 24). If voltage is stays low, go to next step. If voltage stays high, go to step 24).

23) Check HO2SH Circuit For Short To Ground

Turn ignition off. Disconnect suspect HO2S sensor. Install breakout box (leave PCM disconnected). Measure resistance between breakout box test pin No. 83 or 84 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 .

24) Check VPWR Circuit Continuity

Turn ignition off. Disconnect suspect HO2S sensor. Turn ignition on. Measure voltage at VPWR terminal (Blue/Yellow) at 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 .

25) Check HO2S Heater Circuit Continuity

Turn ignition off. Disconnect suspect HO2S sensor. Install breakout box (PCM disconnected). Measure resistance between HO2SH terminal at harness connector of suspect sensor and appropriate breakout box test pin (No. 83 or 84). 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 .

26) Check HO2S Heater

Turn ignition off. Disconnect suspect HO2S. 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.

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.

41) Fuel Pressure Check

Connect fuel pressure gauge to fuel rail or fuel filter. Start engine and observe fuel pressure. If fuel pressure is 34-38 psi (234-262 kPa), go to next step. If fuel pressure is not as specified, go to CIRCUIT TEST HC .

42) Check Fuel Pressure Leakdown

With fuel pressure gauge installed, turn ignition switch on and off several times. Turn ignition off and observe fuel pressure gauge. If fuel pressure drops less than 5 psi in one minute, go to next step. If fuel pressure drops 5 psi or more in one minute, check for external leaks. If no external leakage is found, check fuel injectors, fuel pressure regulator and fuel pump check valve for internal leakage. See CIRCUIT TEST HC .

43) Check Injector Circuit Resistance

Turn ignition off. Disconnect negative battery cable. Disconnect PCM and inspect connector for corroded or pushed out pins etc., repair as necessary. Install breakout box (leave PCM disconnected). Measure resistance between breakout box test pin No. 67 (KAPWR) and fuel injector test pins. See Fig 1. If resistance is 10-14 ohms, circuit is okay, go to step 46). If resistance is not 10-14 ohms, go to next step.

44) Check Injector Harness

Turn ignition off. Breakout box installed (PCM disconnected). Disconnect injector harness connectors. Measure resistance between breakout box test pin No. 67 (KAPWR) and KAPWR terminal at each injector harness connector. See Fig 1. Also measure resistance of each injector signal circuit between appropriate breakout box pins and terminal at each injector harness connector. If all resistances are less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open harness circuit as necessary. Restore electrical connections and repeat QUICK TEST .

45) Check Injector Harness For Short

Turn ignition off. Breakout box installed (PCM connected). Disconnect suspect injector harness connector. Measure resistance between breakout box test pins No. 67 (KAPWR) and 43 (GND) and 50 (SIG RTN). Measure resistance between injector signal pin and ground. If all resistance measurements are greater than 10 k/ohms, go to next step. If any resistance measurement is less than 10 k/ohms, repair shorted circuit. Restore all electrical connections and repeat QUICK TEST .

46) Check Injector Driver

Turn ignition off. Breakout box installed (connect PCM to breakout box). Connect a standard non-powered test light between breakout box test pin No. 67 KAPWR and each injector test pin. See Fig 1. Crank engine. If test light dimly glows while cranking, remove breakout box and go to next step. If test light does not glow or glows brightly, replace PCM. Restore electrical connections and repeat QUICK TEST .

47) 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 CIRCUIT TEST Z . Also check PIDs SHRTFT1, SHRTFT2, LONGFT1, LONGFT2.