Diagnostic Aids

Perform this test when instructed during QUICK TEST or if directed by other test procedures. Only use this test to diagnose.

• Ignition System
• Fuel Pressure
• Fuel Injectors
• Engine Vacuum System
• Evaporative System
• Fuel Vapor Storage Canister
• Canister Purge Solenoid
• Internal Engine Wear
• Crankshaft Position (CKP) Sensor
• Powertrain Control Module (PCM)

1. 1) Check For Adaptive Fuel Monitor & HO2S Continuous Memory DTCs
   
   Check for other non-misfire Continuous Memory DTCs which could cause the misfire DTC. If DTC P0136, P0156, P0171, P0172, P0175, P1130 or P1150 is present, go to step  3). If specified DTCs are not present, go to next step.
2. 2) Check For Any Other Continuous DTCs
   
   Check for other non-misfire Continuous Memory DTCs which could cause the misfire DTC. If no other Continuous Memory DTCs are present, go to next step. If any other Continuous Memory DTCs are present, disregard misfire DTCs at this time and service next Continuous Memory DTC as necessary. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
3. 3) Check For KOEO DTCs
   
   Check for any KOEO DTCs which could cause the misfire DTC. If any KOEO DTCs are present, service DTCs as necessary. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . Disregard misfire DTCs at this time. If any other DTCs are present, perform appropriate system test. If no KOEO DTCs are present, go to TEST JB  to check spark plugs and spark plug wires. If spark plugs and spark plug wires are okay, go to next step.
4. 4) Check For KOER DTCs
   
   If KOER DTC P1131, P1132, P1137, P1138, P1151, P1152, P1157 or P1158 is present, go to step  8). If any other KOER DTCs are present, disregard misfire DTCs at this time and service DTCs as necessary. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  table. If no KOER DTCs are present and a misfire problem is present, go to next step for vehicles equipped with Differential Pressure Feedback (DPF) EGR system, or go to step  7) for vehicles not equipped with DPF EGR system. If misfire problem is intermittent, use FREEZE FRAME DATA MODE  under ADDITIONAL SYSTEM FUNCTIONS, and go to TEST Z . If no KOER DTCs are present and no misfire is present, go to step  7).
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 4) to step 6). No test procedures have been omitted.
5. 6) Check/Compare PID Values
   
   Connect scan tool to Data Link Connector (DLC). Start engine and allow to idle. Ensure engine is warmed to normal operating temperature. Using scan tool, select and record DPFEGR PID voltage reading while engine is running (KOER). Turn ignition switch to OFF position. Turn ignition switch to ON position (KOEO). Select and record DPFEGR PID voltage reading while engine is off. Compare KOEO and KOER DPFEGR PID voltage readings. If DPFEGR PID voltage readings are within .15 volt of each other, go to next step. If DPFEGR PID voltage readings are not within .15 volt of each other, go to TEST HE, step  100).
NOTE: DTCs may be stored during testing and will need to be cleared following repair.
6. 7) EGR Restriction/Flow Test
   Record and clear codes. Disconnect and plug EGR valve vacuum hose. Perform MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLE PROCEDURES  under ADDITIONAL SYSTEM FUNCTIONS. If misfire code is still present, go to next step. If misfire code is no longer present, inspect EGR passage and intake port for blockage and repair as necessary.
7. 8) Check Injector Driver PIDs
   
   Turn ignition switch to ON position. Using scan tool, select and record appropriate injector PID for suspect injector. If injector PID value indicates YES, go to next step. If injector PID value indicates NO, go to step  10).
8. 9) Check Fuel Injector & Circuit Resistance
   
   Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure and record resistance between PCM harness connector suspect fuel injector and VPWR terminals. See Figure. See FUEL INJECTOR PCM TERMINAL IDENTIFICATION  table for PCM injector terminal identification. Fuel injector resistance should be within specification. See FUEL INJECTOR RESISTANCE SPECIFICATIONS  table. If fuel injector resistance is within specification, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE . If fuel injector resistance is not within specification, go to TEST H, step  57).
   FUEL INJECTOR RESISTANCE SPECIFICATIONS
   
   

   Application	Resistance
   Contour & Cougar 2.5L (Except H/O), Escort 2.0L (4V), Focus 2.0L (2V), Mystique 2.5L & Taurus (4V) Flex Fuel Engine E22	13.8-15.2
   Econoline & Pickup 4.2L, Mustang 3.8L & Windstar 3.8L	9-16
   Focus 2.0L (4V) & LS 3.9L (V8)	11.4-12.6
   LS 3.0L (V6)	13-16
   Compressed Natural Gas & Liquid Petroleum Gas Vehicles	4-6
   All Others	11-18

9. 10) Check Fuel Pressure
   
   Turn ignition switch to OFF position. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE procedure in appropriate REMOVAL, OVERHAUL & INSTALLATION article. Install fuel pressure gauge. Start engine and allow to idle. Record initial fuel pressure gauge reading. Increase engine speed to 2500 RPM and maintain for one minute. Record final fuel pressure gauge reading. Compare fuel pressure gauge readings to specification. See FUEL PRESSURE SPECIFICATIONS . If fuel pressure is as specified, turn ignition switch to OFF position and go to next step. If fuel pressure is not as specified, check and repair fuel system as necessary.
10. 11) Check Ability Of Fuel System To Hold Fuel Pressure
    
    Start engine and allow to idle. Note fuel pressure gauge reading. Increase engine speed to 2500 RPM and maintain for one minute. Check for fuel leaking from around fuel injectors, fuel pressure regulator and fuel hoses. Repair as necessary. Turn ignition switch to OFF position and note fuel pressure gauge reading. If fuel pressure remains within 5 psi (35 kPa) of specification for one minute, go to next step. If fuel pressure does not remain within 5 psi (35 kPa) of specification for one minute, check fuel system and repair as necessary.
11. 12) Check Fuel Injector Flow & Leakage
    
    Turn ignition switch to OFF position. Use Rotunda injector tester from Fuel Tester Kit (113-00114) to flow test fuel injectors. Follow injector tester instructions. If flow rate for each fuel injector is okay, fuel delivery system is not the likely cause of misfire DTC. Go to step  20). If flow rate for any fuel injector is not okay, clean or replace defective fuel injector. Perform MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLE PROCEDURES  under ADDITIONAL SYSTEM FUNCTIONS.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 12) to step 20). No test procedures have been omitted.
12. 20) Check Vacuum System
    
    Inspect all vacuum hoses for kinks or damage. Ensure all vacuum connections are clean and tight. Repair as necessary and perform MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLE PROCEDURES  under ADDITIONAL SYSTEM FUNCTIONS. If vacuum system is okay, go to next step.
13. 21) Check Crankshaft Pulley
    
    On models equipped with crankshaft pulley-mounted pulse ring, check crank pulley and pulse ring for damage or looseness. On models not equipped with crankshaft pulley-mounted pulse ring, remove front cover if necessary. Check crank pulley and pulse ring for damage or looseness. On all models, repair as necessary and disconnect battery for 5 minutes to allow PCM to learn new data. If no faults are found, go to next step.
NOTE: The misfire monitor can be affected by the evaporative emission system.
14. 22) Check Evaporative Emission System
    Inspect carbon (charcoal) canister for fuel saturation. Replace carbon canister if canister contains liquid fuel. Perform MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLE PROCEDURES  under ADDITIONAL SYSTEM FUNCTIONS. If carbon canister is okay, go to next step.
15. 23) Pressure Test Evaporative System
    
    Using Rotunda Evaporative Emission System Tester (134-00056), pressure test evaporative system starting at EVAP service port (if equipped) then at fuel filler cap. Follow evaporative emission system tester instructions. If evaporative emission system holds pressure, go to next step. If system does not hold pressure, isolate fault and repair as necessary. Perform MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLE PROCEDURES  under ADDITIONAL SYSTEM FUNCTIONS.
16. 24) Check Vacuum In Evaporative System
    
    Inspect vacuum hoses between engine and carbon canister for restrictions or damage. Ensure all vacuum connections are clean and tight. Check for fuel tank vent system blockage. Repair as necessary. Perform MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLE PROCEDURES  under ADDITIONAL SYSTEM FUNCTIONS. If no faults are found, go to step  26).
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 24) to step 26). No test procedures have been omitted.
17. 26) Check EVAP Canister Purge Control Valve (CPCV) Housing
    
    Turn ignition switch to OFF position. Ensure vehicle is at room temperature. Connect vacuum pump to fuel vapor port at EVAP CPCV and apply 16 in. Hg (53 kPa). If vacuum holds, go to next step. If vacuum releases, replace EVAP CPCV.
18. 27) Check For Filter Contamination
    
    Disconnect hose from vacuum input port of EVAP CPCV. Connect vacuum pump to EVAP CPCV vacuum input port and apply 10-15 in. Hg (48-52 kPa). If little or no vacuum is lost, service EVAP CPCV filter. If filter is okay, replace EVAP CPCV. Perform MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLE PROCEDURES  under ADDITIONAL SYSTEM FUNCTIONS. If vacuum is not as specified, reconnect all components and go to step  29).
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 27) to step 29). No test procedures have been omitted.
19. 29) Check Engine Condition
    
    Inspect engine for obvious faults. Ensure compression is okay. Check PCV system for restrictions or leaks. Repair as necessary. If no faults can be found, misfire trouble code is intermittent. Go to TEST Z  to check intermittent. If okay, go to next step.
20. 30) Check For Additional Misfire DTCs
    
    DTC P0300 indicates multiple cylinders are misfiring or PCM cannot identify which cylinder is misfiring. If any other misfire DTCs are present, go to step  1). If no other misfire DTCs are present, go to next step.
21. 31) Check For Other Continuous Memory DTCs
    
    If any other Continuous Memory DTCs are present, service DTCs as necessary. If no other Continuous Memory DTCs are present, go to next step.
22. 32) Check/Compare PID Values
    
    Connect scan tool to Data Link Connector (DLC). Start engine and allow to idle. Ensure engine is warmed to normal operating temperature. Using scan tool, select and record DPFEGR PID voltage reading while engine is running (KOER). Turn ignition switch to OFF position. Turn ignition switch to ON position (KOEO). Select and record DPFEGR PID voltage reading while engine is off. Compare KOEO and KOER DPFEGR PID voltage readings.
    NOTE: Hall Effect type camshaft position sensor has a 3-pin connector. Variable reluctance type camshaft position sensor has a 2-pin connector.

    If DPFEGR PID voltage readings are within .15 volt of each other, go to step  40) for vehicles with Hall Effect type CMP sensor, or go to step  41) for vehicles with variable reluctance type CMP sensor. If DPFEGR PID voltage is not as specified, go to TEST HE, step  100).

    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 32) to step 40). No test procedures have been omitted.
23. 40) Continuous Memory DTC P1309: Check Hall Effect CMP Sensor Output
    
    This fault indicates MISFIRE MONITOR was disabled due to a CMP sensor input signal to PCM malfunction. Possible causes for this fault are:
    • Camshaft Position (CMP) Sensor
    • CKP, ECT & MAF Sensors
    • Powertrain Control Module (PCM)

    Turn ignition and all accessories off. Ensure CMP sensor is connected. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure voltage between PCM harness connector CMP and PWR GND terminals. See WIRING DIAGRAMS. See Figure or Figure . Using starter, bump engine in short bursts for at least 10 revolutions. DO NOT allow engine to start. If voltage switches from less than 2 volts to more than 8 volts, check CMP sensor for correct installation. If sensor is correctly installed (synchronized), replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE . If voltage does not switch from less than 2 volts to more than 8 volts, replace CMP sensor.

24. 41) Continuous Memory DTC P1309: Check Variable Reluctance CMP Sensor Output
    
    This fault indicates MISFIRE MONITOR was disabled due to CMP sensor input signal to PCM malfunction. Possible causes for this fault are:
    • Camshaft Position (CMP) Sensor
    • CKP, ECT & MAF Sensors
    • Powertrain Control Module (PCM)

    Turn ignition and all accessories off. Ensure PCM is connected. Using a DVOM, backprobe and measure A/C voltage between PCM harness connector CMP and PWR GND terminals. See WIRING DIAGRAMS. See Figure or Figure . Start engine and vary engine speed. If A/C voltage does not vary more than .1 volt, replace CMP sensor. If A/C voltage varies more than .1 volt, check CMP sensor for correct installation. If CMP sensor is correctly installed, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE .