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Diagnostic Aids

WARNING: This page is about a different car, the 1995 Ford Explorer and 1995 Ford Aerostar. However, it is still accessible from the selected car via links, so may be relevant.

Perform this test only when instructed during QUICK TEST or if directed by other test procedures. This CIRCUIT TEST is intended to diagnose:

To prevent replacement of good components, be aware the following non-EEC components may be at fault:

Fig 1: DPFE Sensor Connector Terminal ID (Explorer)
G95F12935
Fig 2: Identifying EVR Solenoid Connector Terminals (4.0L)
G95H26853
DPFE SENSOR SPECIFICATIONS

Pressure (psi) Vacuum (In. Hg) (1) Volts
4.34 8.83 4.56
3.25 6.62 3.54
2.17 4.41 2.51
1.08 2.21 1.48
0 0 0.45
(1) Values may vary by 15 percent.

1) Code 327: Generate Code 337  Code 327 indicates DPFE sensor signal is less than self-test minimum of 0.2 volt. Possible causes for this fault are:

Turn ignition off. Disconnect DPFE wiring harness connector at sensor. Install a jumper wire between VREF circuit and DPFE circuit at sensor wiring harness connector. Perform KOEO SELF-TEST. If no codes are present, remove jumper wire and go to step 4). If Code 337 is present, ignore all other codes and replace DPFE sensor. Repeat QUICK TEST. If Code 337 is not present, remove jumper wire and go to next step.

2) Measure VREF Circuit Voltage  With DPFE sensor disconnected, turn ignition on. Measure voltage between sensor wiring harness connector VREF and SIG RTN terminals. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to CIRCUIT TEST C.

3) Check DPFE Circuit Continuity  Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between DPFE terminal at sensor wiring harness connector and test pin No. 27 at breakout box. If resistance is more than 5 ohms, repair open circuit. Repeat QUICK TEST. If reading is 5 ohms or less, go to next step.

4) Check DPFE Circuit For Shorts To Ground & SIG RTN  Turn ignition off. Measure resistance between test pin No. 27 and test pins No. 40, 46 and 60 at breakout box. If any resistance is less than 10,000 ohms, repair short circuit. Repeat QUICK TEST. If all resistance readings are 10,000 ohms or more, replace PCM. Repeat QUICK TEST.

5) Code 337: Generate Code 327  Code 337 indicates DPFE sensor signal is greater than self-test maximum of 4.8 volts. Possible causes for this code are:

Turn ignition off. Disconnect DPFE sensor. Repeat KOEO SELF-TEST. Check for Code 327. Ignore all other codes at this time. If Code 327 is not present, go to step 7). If Code 327 is present, go to next step.

6) Measure VREF Circuit Voltage  With DPFE sensor disconnected, turn ignition on. Measure voltage between VREF and SIG RTN terminals at DPFE sensor wiring harness connector. If reading is 4-6 volts, replace DPFE sensor. Repeat QUICK TEST. If reading is not 4-6 volts, go to CIRCUIT TEST C.

7) Check DPFE Circuit For Short To Power  With ignition off, disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 27 and test pins No. 26, 37 and 57. If any resistance reading is less than 10,000 ohms, repair short circuit. Repeat QUICK TEST. If all resistance readings are 10,000 ohms or more, replace PCM. Repeat QUICK TEST.

8) Code 335: Verify KOER Codes  Code 335 indicates DPFE sensor is out of self-test range (2.6-4.2 volts) and may be faulty. DPFE system can detect lack of pressure in exhaust system. A garage exhaust ventilation system, installed during KOEO SELF-TEST, may cause DPFE sensor to generate Code 335. Remove exhaust ventilation system. Repeat KOEO SELF-TEST. Service codes as necessary. If no codes are present during KOEO SELF-TEST, complete QUICK TEST. If Code 335 is present during KOEO SELF-TEST, go to next step.

9) Check DPFE Sensor Pressure Input Hose  Remove pressure feed tube from DPFE sensor. Inspect tube, including DPFE inlet, for blockage. Repair if necessary, and repeat QUICK TEST. If no blockage is found, go to next step.

10) Measure VREF Circuit Voltage  With ignition off, disconnect DPFE sensor wiring harness connector. Turn ignition on. Measure voltage between VREF and SIG RTN terminals at DPFE sensor wiring harness connector. If voltage is 4-6 volts, replace DPFE sensor and repeat QUICK TEST. If reading is not 4-6 volts, go to CIRCUIT TEST C.

11) Code 558: Measure EVR Solenoid Resistance  Code 558 indicates failure in EVR solenoid or circuit. Possible causes for this code are:

Turn ignition off. Disconnect EVR solenoid connector. Measure resistance between terminals. If resistance is 20-70 ohms, go to next step. If resistance is not 20-70 ohms, replace EVR solenoid. Repeat QUICK TEST.

12) Check VPWR Circuit Voltage  Turn ignition on. Measure voltage between VPWR terminal at EVR solenoid wiring harness connector and negative battery terminal. If voltage is less than 10.5 volts, repair open circuit and repeat QUICK TEST. If voltage is 10.5 volts or more, go to next step.

13) Check EVR Circuit Continuity  Turn ignition off. Leave EVR solenoid connector disconnected. Disconnect PCM 60-pin connector. Inspect terminals and repair if damaged. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between EVR terminal at EVR solenoid wiring harness connector and test pin No. 33 at breakout box. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.

14) Check EVR Circuit For Short To Power Or Ground  Turn ignition off. Measure resistance between test pin No. 33 and pins No. 37, 40, 57 and 60 at breakout box. If any resistance reading is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If code is repeated, replace PCM. If all readings are 10,000 ohms or more, replace PCM and repeat QUICK TEST.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 14) to step 21). No test procedures have been omitted.

21) Code 327  Code 327 indicates DPFE sensor signal is less than self-test minimum. Disconnect and plug EGR valve vacuum hose. Perform KOER SELF-TEST. If Code 326 or 327 is present, go to next step. If codes are not present, check EVR vent and vacuum hose to EGR valve for blockage. Repair as necessary. If vent and vacuum hose are okay, replace EVR solenoid and repeat QUICK TEST.

22) Code 326 Or 327: Check DPFE Input Hoses  With ignition off, check DPFE sensor pressure input hose for blockage and leaks. Repair as necessary. Connect all lines, and repeat QUICK TEST. If no fault is found, go to next step.

23) Check DPFE Voltage With Engine At Idle  Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals and repair if damaged. Install Breakout Box (T83L-50-EEC-IV). Leave PCM connected to breakout box. Start engine and allow to idle with transmission in Park or Neutral. Measure voltage between test pins No. 27 and 46 at breakout box. If voltage is less than 0.2 volt, replace sensor and repeat QUICK TEST. If voltage is more than 0.2 volt, replace PCM and repeat QUICK TEST.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 23) to step 30). No test procedures have been omitted.

30) Code 332: Verify Vacuum At EGR Valve  Code 332 indicates DPFE sensor input to PCM did not change after EVR solenoid received signal from PCM to open EGR valve. Possible causes for this fault are:

Turn ignition off. Using a vacuum "T", connect vacuum gauge at EGR valve. Perform KOEO SELF-TEST while observing vacuum gauge. Disregard code output at this time. If vacuum reading is greater than one in. Hg, go to step 34). If vacuum reading is one in. Hg or less, remove vacuum gauge and go to next step.

31) Check Vacuum Input To EVR Solenoid  Turn ignition off. Disconnect EVR vacuum hose. Connect EVR vacuum hose to vacuum gauge. Start engine and allow to idle while observing vacuum gauge. If 15 in. Hg. or more is present, replace EVR solenoid and repeat QUICK TEST. If less than 15 in. Hg. is present, repair vacuum source and repeat QUICK TEST.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 31) to step 34). No test procedures have been omitted.

34) Check Vacuum At DPFE Inlet Hose(s)  Turn ignition off. Inspect vacuum hose for damage and repair if necessary. Using a vacuum "T", connect vacuum gauge at DPFE inlet hose(s). Perform KOEO SELF-TEST while observing vacuum gauge. If vacuum momentarily increases, go to next step. If momentary increases in vacuum do not occur, service EGR valve.

35) Attempt To Generate KOEO Code 337  Turn ignition off. Disconnect DPFE sensor. Install jumper wire between DPFE terminal and VREF terminal at DPFE sensor wiring harness connector. Perform KOEO SELF-TEST. If Code 337 is present, ignore all other codes. Replace DPFE sensor and repeat QUICK TEST. If Code 337 is not present, remove jumper wire and go to next step.

36) Measure VREF Circuit Voltage  With DPFE sensor disconnected, turn ignition on. Measure voltage between VREF terminal and SIG RTN terminal at DPFE sensor wiring harness connector. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to CIRCUIT TEST C.

37) Check DPFE Circuit Resistance  Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between DPFE terminal at DPFE sensor wiring harness connector and test pin No. 27 at breakout box. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.

38) Check DPFE Circuit For Short To SIG RTN & Ground  Turn ignition off. Measure resistance between DPFE terminal at DPFE sensor wiring harness connector and test pins No. 40, 46 and 60 at breakout box. If any resistance checks are less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If all resistance checks are 10,000 ohms or more, replace PCM and repeat QUICK TEST.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 38) to step 50). No test procedures have been omitted.

50) Codes 336 & 337: Check EVR Malfunction  Code 336 indicates DPFE voltage is too high at zero duty cycle. Possible causes for these codes are:

Disconnect and plug EGR vacuum hose. Perform KOEO SELF-TEST. If Code 336 or 337 is present, go to next step. If Code 336 or 337 is not present, ensure vacuum hose routing is correct and EVR filter is clean. If okay, replace EVR solenoid.

51) Check DPFE Sensor Output With Engine Idling  Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Start engine and allow to idle with transmission in Park or Neutral. Measure voltage between test pins No. 27 and 46 at breakout box. If voltage is less than 0.7 volt at idle, replace PCM and repeat QUICK TEST. If voltage is 0.7 volt or more, go to next step.

52) Check EGR Valve  Remove EGR valve. Check EGR valve for carbon deposits, binding or other damage. Repair as necessary. Install EGR valve and repeat KOEO SELF-TEST. If Code 336 or 337 is still present, replace EGR valve and repeat KOER SELF-TEST. If Code 336 or 337 is still present, replace DPFE sensor and repeat QUICK TEST. If Code 336 or 337 is not present, fault is intermittent and cannot be duplicated at this time. Testing is complete.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 52) to step 90). No test procedures have been omitted.

90) EGR Fault Code(s) In Continuous Memory  Repeat QUICK TEST. If fault code(s) are present, go to appropriate circuit test. If fault codes are present in continuous memory only, go to next step.

91) DPFE System Inspection  Check for damaged or loose connectors. Check for loose or corroded connector pins. Inspect wiring harness for proper routing and insulation. Ensure component mounting and vacuum hose routing are correct. Ensure EVR solenoid filter is clean. Repair or replace as necessary and repeat QUICK TEST. If no faults are present, go to next step.

92) EGR Fault Code(s) In Continuous Memory  Repeat QUICK TEST. If fault code(s) is present, go to appropriate circuit test. If fault code 326, 327, 336 or 337 is present in continuous memory only, go to next step. If fault Code 332 is present in continuous memory only, go to step 105).

93) Continuous Memory Code 326, 327, 336 Or 337  If code is present, possible causes are:

Enter wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST)  under QUICK TEST. Observe analog VOM or diagnostic tester for indication of fault while performing following steps. Grasp wiring harness near sensor connector while observing VOM or diagnostic tester for fault indication. Shake and bend small sections of harness, working from sensor toward firewall. Shake and bend harness from firewall to PCM. If fault is indicated, inspect connectors and terminals. Repair as necessary. If connectors and terminals are okay, replace PFE/DPFE sensor. Clear codes and repeat QUICK TEST. If no fault is indicated, go to next step.

94)  Stay in wiggle test. Observe analog VOM or scan tester for indication of fault while bending or wiggling small sections of harness from sensor connector to firewall, and from firewall to PCM. If fault is indicated, isolate fault in harness and repair as necessary. Repeat QUICK TEST. If no fault is indicated, go to next step.

95) Check PCM Wiring Harness Connector  Turn ignition off, and wait 10 seconds. Disconnect PCM 60-pin connector. Inspect connector and terminals for damage and repair as necessary. Clear codes, and repeat QUICK TEST. If connector and terminals are okay but fault Code 326 or 327 is present, go to next step. If no codes are present, fault is intermittent and cannot be duplicated at this time. Testing is complete.

96) Check EGR Valve Operation  Turn ignition off. Disconnect vacuum hose from EGR valve. Connect vacuum pump to EGR valve. While observing EGR valve, slowly apply 10 in. Hg and release. If EGR valve does not operate smoothly, service or replace EGR valve. Repeat QUICK TEST. If EGR valve operation is smooth, go to next step.

97) Check EVR Solenoid & Hoses  Turn ignition off. Inspect EVR solenoid vacuum hoses for contamination, moisture or restriction. Ensure EVR solenoid filter is clean. Repair or replace as necessary, and repeat QUICK TEST. If no faults are found, go to next step.

98) Check EVR Solenoid For Short Circuit  Turn ignition off. Disconnect vacuum hose from EGR valve. Connect vacuum pump to vacuum hose. Start engine and operate at idle. While observing vacuum gauge, tap on EVR solenoid and wiggle wiring harness connector. If vacuum gauge does not remain less than one in. Hg and has erratic increases, replace EVR solenoid and repeat QUICK TEST. If vacuum gauge remains less than one in. Hg with no erratic increases, leave vacuum gauge connected and go to next step.

99) Check Wiring Harness Between EVR Solenoid & PCM  With engine running, observe vacuum gauge while wiggling wiring harness connector between EVR solenoid and dash panel. Wiggle wiring harness between dash panel and PCM. If EGR vacuum increases, isolate short and repair as necessary. Repeat QUICK TEST. If EGR vacuum does not increase, fault is intermittent and cannot be duplicated at this time. Testing is complete.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 99) to step 101). No test procedures have been omitted.

101) Check EGR Vacuum At Start-Up  Disconnect and plug EGR vacuum hose. Start engine and allow to idle (if possible). If engine idle is correct, ensure EVR hoses are correctly routed. If hoses are okay, replace EVR solenoid. Clear codes and repeat QUICK TEST. If engine does not idle correctly, go to next step.

102) Check EGR Valve Operation  Turn ignition off. Disconnect vacuum hose from EGR valve. Connect vacuum pump to EGR valve. While observing EGR valve, slowly apply 10 in. Hg and release. If EGR valve does not operate smoothly or close completely, service or replace EGR valve. If EGR valve operation is okay, problem is not EGR related. Connect all components and repeat QUICK TEST.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 102) to step 105). No test procedures have been omitted.

105) Continuous Memory Code 332  Turn ignition off. Disconnect vacuum hose from EGR valve. Connect vacuum pump to EGR valve. While observing EGR valve, apply 1.0-1.5 in. Hg. EGR valve should begin to open. Increase vacuum pump application to 4 in. Hg. EGR valve should be fully open. Increase vacuum pump application to 10 in. Hg. EGR valve should hold and maintain vacuum. If EGR valve does not perform as specified, repair or replace as necessary. Repeat QUICK TEST. If EGR valve is okay, go to next step.

106) Inspect EVR Solenoid Hoses  With ignition off, remove EVR vacuum hoses. Inspect vacuum hoses for damage or restrictions. Repair as necessary. Repeat QUICK TEST. If EVR vacuum hoses are okay, go to next step.

107) Inspect DPFE Hoses  With ignition off, remove DPFE hoses from sensor. Inspect hoses for contamination, leaks or restrictions. Repair as necessary. Repeat QUICK TEST. If DPFE hoses are okay, go to next step.

108) Check EVR Solenoid  Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Disconnect vacuum hose from EGR valve. Connect EGR vacuum hose to vacuum pump. Start engine and allow to idle. Connect jumper wire between test pins No. 33 and 40. EVR solenoid should turn on. Observe vacuum gauge while tapping on EVR solenoid. Wiggle wiring harness and connector. A sudden drop in vacuum indicates a fault in the system. If a sudden drop in vacuum occurs, isolate fault and repair as necessary. Repeat QUICK TEST. If no drop in vacuum occurs, problem cannot be identified at this time. Testing is complete.

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