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Test E: Electronic Pressure Control (EPC) Solenoid

  1. AX4N Electronic Diagnostics  Ensure transaxle harness connector is in acceptable condition. Repair as necessary. Ensure transaxle harness connector is fully seated. Connect NGS tester or equivalent to DLC. Perform KOEO test until Continuous Memory trouble code(s) have been displayed. See QUICK TEST  . Enter output test mode. See ADDITIONAL SYSTEM FUNCTIONS. Select ALL ON mode. Push START to turn outputs ON. Push STOP to outputs OFF. If vehicle enters output state, go to next step. If vehicle will not enter output state, see appropriate TESTS W/CODES article in the ENGINE PERFORMANCE section.
  2. Check Electrical Signal Operation  Turn ignition off. Disconnect transaxle harness connector. Inspect condition of connector and repair as needed. Turn ignition on. Using DVOM, connect positive lead to transaxle harness connector terminal No. 7. See Figure . Connect negative lead to terminal No. 10. While monitoring DVOM, press START and STOP to cycle solenoid output on and off. If voltage changes at least .5 volt, go to step 5). If voltage is unaffected, go to next step.
  3. Check Continuity Of Solenoid Signal & VPWR Harness Circuits  Ensure ignition is off. Disconnect PCM 104-pin connector, and inspect it for damaged pins, corrosion and loose wires. Repair as necessary. Install breakout box, leaving PCM disconnected. Measure and record resistance between test pins No. 71 and 97 and transaxle harness connector terminals No. 2 and 7. Measure and record resistance between test pin No. 81 and transaxle harness connector terminal No. 10. If any resistance is greater than 5 ohms, repair open circuit. Connect all components. Disconnect breakout box and repeat QUICK TEST  . If each resistance is 5 ohms or less, go to next step.
  4. Check Solenoid Harness For Shorts To Power & Ground  Measure and record resistance between breakout box test pin No. 81 and test pins No. 71 and 97. Measure and record resistance between chassis ground and test pin No. 81 and between test pins No. 24, 51, 76, 77, 91 and 103. If any resistance is less than 10 k/ohms, repair short circuit. Connect all components. Disconnect breakout box and repeat QUICK TEST  . If each resistance is 10 k/ohms or more, go to next step.
  5. EPC Functional Test  Connect PCM 104-pin connector. Disconnect transaxle harness connector. Connect transaxle tester. Connect line pressure gauge. See FORD AX4N overhaul article. Set Bench/Drive switch to DRIVE position. Set Gear Selector switch to "1" position. Perform EPC function test. See tester instructions. Observe line pressure on gauge while depressing EPC switch with KOER. EPC solenoid should activate (Green LED) and line pressure should drop when EPC switch is depressed. If solenoid operates correctly, replace PCM. Connect all components. Erase all trouble codes. See CLEARING CODES  . Repeat QUICK TEST  . If solenoid is not operating, go to next step.
  6. Check Resistance Of Solenoid  Ensure tester power is off. Connect ohmmeter to EPC jacks. If resistance is 3.23-5.50 ohms, go to next step. If resistance is not within specifications, go to step 8).
  7. Check Solenoid For Short To Ground  Check continuity between BAT(-) jack of Transmission Tester and EPC jacks. If continuity exists, go to next step. If continuity does not exist, see TROUBLE SHOOTING in FORD AX4N overhaul article.
  8. AX4N Internal Electronic Diagnostics  Drain transaxle fluid. Remove transaxle side cover. Inspect all internal harness connectors. Ensure all connectors are fully connected and not damaged. Repair as needed. If all connectors are okay, go to next step. Install all components in reverse order of disassembly. Fill transaxle with fluid. Erase all DTCs. See CLEARING CODES  . Repeat QUICK TEST  .
  9. Check Internal Transmission Harness Continuity  Disconnect internal harness from EPC solenoid. Connect positive lead of ohmmeter to tester EPC jack and negative lead to EPC connector Blue wire. Measure and record resistance. Connect positive lead of ohmmeter to tester VPWR jack and negative lead to EPC connector Green wire. If resistances measured are .5 ohm or less, go to next step. If any resistance measured is more than .5 ohm, replace internal harness. Go to step 12).
  10. Check Internal Harness For Shorts To Ground  Using transmission tester, check continuity between each EPC solenoid connector terminals and BAT (-) terminal of tester. If continuity does not exist in either circuit, go to next step. If continuity exists in any circuit, replace internal harness. Go to next step.
  11. Check EPC Solenoid Resistance  Using ohmmeter, check resistance between terminals of EPC solenoid. Resistance should be 3.23-5.5 ohm. If resistance is within specification, go to next step. If resistance is not within specification, replace EPC solenoid. Install all components in reverse order of disassembly. Fill transaxle with fluid. Erase all DTCs. See CLEARING CODES  . Repeat QUICK TEST  .
  12. Check Solenoid For Short To Ground  Using ohmmeter, check continuity between each EPC solenoid terminal and ground. If continuity exists, replace faulty EPC solenoid. Install all components in reverse order of disassembly. Fill transaxle with fluid. Erase all DTCs. See CLEARING CODES  . Repeat QUICK TEST  . If continuity does not exist, install all components in reverse order of disassembly. Fill transaxle with fluid. Erase all DTCs. See CLEARING CODES. Repeat QUICK TEST. See TROUBLE SHOOTING in FORD AX4N overhaul article for non-electronic symptom diagnostics.
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