cobra
these are the basic tests from ford manual on o2 sensors
each test is for a cause for the code...
2003 PCED OBD SECTION 5: Pinpoint Tests
Procedure revision date: 07/01/2003
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H: Fuel Control H: Introduction
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H20 PERFORM KOER SELF-TEST
Key on, engine running and engine at operating temperature.
Activate Key On, Engine Running (KOER) Self-Test.
Is DTC P0040, P0041, P1127, P1128, P1129 or P2278 present during KOER Self-Test?
Yes No
GO to Section 4, Powertrain Diagnostic Trouble Code (DTC) Charts and SERVICE DTC P0040, P0041, P1127, P1128, P1129 or P2278. 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 Diagnostic Monitoring Test Results.)
Is the indicated value greater than the minimum threshold?
Yes No
COMPLETE PCM Reset to clear DTCs. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2, Drive Cycles ). GO to H20 . If test results indicate a pass, testing is complete. 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 No
REPAIR source of air leak. COMPLETE PCM Reset to clear DTCs. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2, Drive Cycles ). 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.
Note: If viewing the HO2S11 (O2S11) PID on the 2.3L Focus, the engine must be running.
Is the voltage greater than 1.50 volts?
Yes No
KEY OFF. REPLACE HO2S. CHANGE oil/filter. COMPLETE PCM Reset to clear DTCs. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2, Drive Cycles ). KEY OFF. REMOVE jumper wire. GO to H25 .
H25 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.
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.
Disconnect PCM.
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 No
GO to H26 . REPAIR open circuit. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2, 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 No
GO to H27 . 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 No
REPAIR source of contamination. REPLACE HO2S and oil/filter. COMPLETE PCM Reset to clear DTCs. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2, Drive Cycles ). If diagnosing DTC P0141 or P0161, GO to H30 . 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 No
REPLACE HO2S. REPAIR as necessary.
H30 DTCS P0135 AND P0155, P0141 AND P0161: HO2S HEATER CIRCUIT IS SHORTED TO GROUND, SHORTED TO VPWR OR OPEN CIRCUIT.
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
DTC P0141 = HO2S HTR-12
DTC P0161 = HO2S HTR-22
DTC P0147 = HO2S HTR-13
DTC P0167 = HO2S HTR-23
If PCM was disconnected during a previous Pinpoint Test, reconnect PCM now.
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 No
REPAIR any concerns found during inspection. GO to H31 .
H31 PERFORM KEY ON ENGINE OFF (KOEO) SELF-TEST
Key on, engine off.
Perform KOEO Self-Test.
Are any of the following DTCs present: P0135, P0141, P0147, P0155, P0161, P0167?
Yes No
KEY OFF. GO to H32 . KEY OFF. GO to H33 .
H32 CHECK VPWR VOLTAGE TO H02S HARNESS CONNECTOR
Note: If DTCs P0135 and P0155, P0141 and P0161 or P0147 and P0167 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 No
KEY OFF. GO to H33 . CHECK fuse in circuit. If fuse is OK, REPAIR open VPWR or SIG RTN circuit.
For no VPWR on LS6, LS8 and Thunderbird:
GO to B5 .
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 No
GO to H34 . 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 No
GO to H35 . REPAIR open or excessive resistance in the heater circuit in harness.
H35 CHECK HO2S HTR RESISTANCE
Measure the resistance between HO2S HTR pin and VPWR pin at the HO2S connector (refer to schematic at the beginning of this Pinpoint Test).
Is the resistance between 3 and 30 ohms?
Yes No
GO to H36 . 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.
Is the resistance greater than 10,000 ohms?
Yes No
REPLACE PCM(refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) ). REPLACE HO2S.
H40 DTCs P1131, P1132, P1151, P1152, P2195, P2196, P2197 AND P2198: 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 = DTCs P1131, P1132, P2195 and P2196
HO2S-21 = DTCs P1151, P1152, P2197 and P2198
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 No
REPAIR as necessary. GO to DC25 .
H41 DTCs P0171, P0172, P0174 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 = 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 integrity of the PCV system.
Check fuel delivery system and filter for restriction.
Check for vacuum leaks.
Were any concerns found during inspection?
Yes No
REPAIR as necessary. COMPLETE KAM Reset. GO to DC25 .
H42 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 P0040, P0041, P1127, P1128, P1129, P1131, P1132, P1151, P1152, P2195, P2196, P2197 or P2198 present?
Yes No
KEY OFF. If DTC P0040, P0041, P1127, P1128 or P1129 is present, GO to Section 4, Powertrain Diagnostic Trouble Code (DTC) Charts and REPAIR those DTCs first.
DTCs (P1131, P2195) or (P1151, P2197):
GO to H43 .
DTCs (P1132, P2196) or (P1152, P2198):
GO to H49 . KEY OFF. For Continuous Memory DTCs Only P0171, P0174, P0172 and P0175:
GO to H52 .
If DTC(s) P1132, P2196and/or P1152, P2198 are no longer present, RECONNECT fuel vapor line.
Vehicles experiencing KOER DTC P1131, P1132, P1151, P1152, P2195, P2196, P2197 or P2198: REFER to Evaporative Emissions, Section 303-13 in the Workshop Manual for system leakage.
All others without recurring DTCs:
Unable to duplicate or identify fault at this time. GO to Z1 .
H43 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 H47 (check fuse in the heater circuit).
Jumper the HO2S SIG circuit to the VPWR circuit at the HO2S vehicle harness connector.
Note: If viewing the HO2S11 (O2S11) PID on the 2.3L Focus, the engine must be running.
Is the reading 1.30 volts or greater?
Yes No
KEY OFF. CHECK SIG RTN circuit. GO to H44 . KEY OFF. GO to H46 .
H44 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 No
Reconnect HO2S, GO to H52 . GO to H45 .
H45 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 No
REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) ). REPAIR open circuit.
H46 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 No
GO to H47 . REPAIR open circuit.
H47 CHECK HO2S 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 No
GO to H48 . REPAIR short circuit.
H48 CHECK HO2S 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 PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) ). REPLACE HO2S.
H49 HO2S CIRCUIT CHECK (FOR RICH DTCS)
Disconnect the HO2S related to the DTC received.
Key on.
Access the correct HO2S PID(s).
Note: If viewing the HO2S11 (O2S11) PID on the 2.3L Focus, the engine must be running.
Is the reading 0.2 volt or less?
Yes No
KEY OFF. GO to H51 . KEY OFF. GO to H50 .
H50 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
REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) ). REPAIR short circuit.
H51 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 No
KEY OFF. GO to H52 . KEY OFF. REPLACE HO2S.
H52 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.
Connect battery charger.
Install fuel pressure gauge.
Key on, engine off.
Access Output Test Mode and run the fuel pump to obtain maximum fuel pressure.
NOTE: The fuel pump will only operate for approximately 8 seconds when Output Test Mode is selected and activated. (GO to Pinpoint Test HC to refer to the Fuel Delivery System Test Information Chart.)
Is the fuel pressure within range for the vehicle being diagnosed?
Yes No
KEY OFF.
GO to H53 . KEY OFF. GO to HC1 .
H53 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 No
GO to H54 . Check fuel system for external leaks.
If external leak is detected, GO to HC1
If no external leak is detected, GO to H55
H54 CHECK FUEL SYSTEM FOR PRESSURE STABILITY WITH KEY ON — SLOW 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 one minute?
Yes No
For HO2S DTCs displayed with misfire DTCs:
GO to H56 .
All other DTCs: GO to H59 GO to HC5 .
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H55 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 P0210 or an injector(s) fault present?
Yes No
GO to H56 . For DTCs P0300 through P0310:
GO to HD12 .
For all other DTCs: GO to H59 .