Circuit Test D12

Fig 1: IDM Circuit

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

• TFI or DIS ignition module.
• Ignition coil or DIS coil packs.
• Spark plugs and/or high tension cables.
• Distributor and PIP sensor.
• Secondary ignition component arcing.

This test is intended to diagnose the following circuits and components.

• Harness circuits: IGNITION GROUND, SPOUT, PIP, IDM & DPI
• ECA assembly

There are 3 types of ignition system connections used with EEC-IV. They are configured as follows:

• Distributorless Ignition System (DIS)  - Two 6-pin connectors located at top and bottom of DIS module. Pins No. 1-6 are located on the top of the module. Pins No. 7-12 are located in the connector on the bottom of the module.
• Closed Bowl Distributor (CBD)  - TFI module is located on the cowl, away from the distributor. The previous mounting window in the bowl of the distributor is closed. Two connectors are used, one connecting the harness to the vehicle Hall sensor, located in the distributor, and another connecting the harness to the TFI module.
• TFI Module Distributor  - This is the most common system. The TFI module is mounted in the distributor and a single module connector is used.
  IGNITION SYSTEM APPLICATIONS
  
  

  Vehicle	Application
  3.8L SC SEFI	DIS
  3.8L RWD SEFI & 3.8L AXOD SEFI	CBD

1. Code 14: Erratic Ignition. Code 14 indicates two successive erratic Profile Ignition Pickup (PIP) pulses occurred, resulting in a possible engine miss or stall. Possible causes for this fault are: loose wires or connectors, arcing secondary ignition components or on-board transmitter equipment (2-way radio). If any of the above are present, service as necessary, clear code and rerun QUICK TEST. If the items listed are not present, go to step 3).
2. Check For Other Codes. If Codes 45, 46 or 48 are present, go to step 12). If Codes 45, 46 or 48 are not present, go to next step.
3. Continuous Memory Codes 14, 18, 28 or 48: Check IDM Circuit Continuity. Code 18 indicates a loss of IDM input signal. Possible causes:
   • Open harness circuit
   • Shorted harness
   • Faulty TFI or DIS module
   • Faulty ECA

   Code 28 indicates IDM input signal always low. Possible causes:

   • Open or shorted harness
   • Faulty CID sensor
   • VBAT (battery voltage) low at DIS
   • Faulty DIS module
   • Faulty ECA

   Code 48 indicates IDM input signal always high. Possible causes:

   • Open signal in harness
   • VBAT open at secondary coil
   • VBAT low at secondary coil
   NOTE: On TFI vehicles the IDM circuit has a 22K-ohm resistor between test pin No. 4 and the ignition coil negative terminal.

   Turn key off an wait 10 seconds. Disconnect E-core ignition coil on TFI vehicles and DIS module connector (pins No. 7-12) on DIS equipped vehicles. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leave ECA connected and set DVOM on 200K-ohm scale.

   On TFI equipped vehicles, measure resistance between test pin No. 4 at the breakout box and negative terminal of ignition coil harness connector. On DIS equipped vehicles, measure resistance between test pin No. 4 at the breakout box and DIS module harness connector pin No. 12.

   If resistance is between 20K and 24K ohms, go to next step. If resistance is not to specification, repair open circuit, clear codes, retest and reconnect E-core coil.

4. Checking IDM Circuit For Short to Ground. Turn key off and wait 10 seconds. Disconnect E-core ignition coil on TFI vehicles and DIS module connector (pins No. 7-12) on DIS equipped vehicles. Install breakout box and ECA disconnected. With DVOM on 200K-ohm scale, measure resistance between test pin No. 4 and test pins No. 40, 46, and 60. If any reading is less than 10K ohms, repair short to ground in IDM circuit, reconnect all components and rerun QUICK TEST. If all readings are 10K ohms or more, reconnect components and go to next step.
5. Checking ECA For Short to Ground. Turn key off and wait 10 seconds. Disconnect E-core ignition coil on TFI vehicles and DIS module connector (pins No. 7-12) on DIS equipped vehicles. Install breakout box and connect ECA. With DVOM on 200K-ohm scale, measure resistance between test pin No. 4 and test pins No. 40, 46, and 60. If any reading is less than 10K ohms, replace ECA, reconnect all components and rerun QUICK TEST. If all readings are 10K ohms or more, reconnect components and go to next step.
6. Checking Ignition Module. Turn key off and wait 10 seconds. Deactivate SELF-TEST. Using CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while lightly tapping on TFI or DIS module to simulate road shock. Wiggle TFI or DIS harness connectors. On Closed Bowl Distributor (CBD) models, wiggle TFI and distributor hall connectors. If fault is indicated, disconnect and inspect TFI harness connectors and terminals for damage. If connector and terminals are okay, check TFI ignition system, if ignition is okay, replace ECA. If no fault is indicated, go to next step.
7. Checking EEC-IV Harness. While in CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while wiggling, shaking, or bending small sections of harness while working from TFI or DIS connector toward firewall. Repeat process from firewall to ECA. On CBD systems also test distributor Hall connector. Perform this test to check for faults in the following circuits:
   • PIP Open/Shorted to Ground: Check circuit at test pin No. 56.
   • SPOUT Shorted to Ground: Check circuit at test pin No. 36.
   • Ignition Ground Open: Check circuit at test pin No. 16.
   • IDM Open to Ground: Check circuit at test pin No. 4.
   • IDM Shorted to Power: Check circuit at test pin No. 4.

   Perform CONTINUOUS MONITOR (WIGGLE) TEST on these circuits one at a time in order to isolate fault. If fault is indicated, isolate fault and repair harness. Repeat QUICK TEST. If no fault is indicated, go to next step.

8. Checking ECA and Harness Connectors. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion or loose wires. If connector is damaged, repair as necessary, clear codes and repeat QUICK TEST. If connector is okay, perform the following procedure based on the Continuous Memory Code displayed:
   • Code 14: Unable to duplicate erratic ignition fault in EEC system. Remove breakout box, reconnect all components. Diagnosis DIS ignition system.
   • Code 18: Replace ECA, remove breakout box and reconnect all components. Start and run engine for about one minute and rerun QUICK TEST.
   • Codes 28 and 48: Remove breakout box and reconnect all components. Diagnose ignition system. If ignition system is okay, replace ECA.
9. Continuous Memory Code 19: Check Camshaft Sensor Output. Code 19 indicates one of the 2 Cylinder Identification (CID) sensor output signals has failed. One of the outputs is a signal sent to the DIS and the second output is the signal to the ECA. Both outputs have a 50% duty cycle of 0.4 volt to battery voltage (VBAT). Possible causes for this fault are; open or short in CID-to-ECA circuit. With key off, disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion or loose wires. If connector is damaged, repair as necessary. Install breakout box and connect ECA. With KOER, and DVOM set on AC scale, measure voltage between test pin No. 24 and GROUND. If voltage varies, replace ECA, remove breakout box, reconnect all components and rerun QUICK TEST. If voltage does not vary, go to next step.
NOTE: This test procedures has been revised based on updated procedures in Ford Technical Service Bulletin, 91-11B-5.
10. Check CID Harness For Continuity. With key off and breakout box installed, disconnect ECA. Disconnect camshaft sensor. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 24 at the breakout box and CID circuit at the camshaft sensor vehicle harness connector. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open circuit, remove breakout box, reconnect all components and rerun QUICK TEST.
11. Check CID Circuit For Shorts. Turn key off, Install breakout box, disconnect ECA and camshaft sensor. Disconnect DIS module (Pin 1-6). Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 24 and test pins No. 16, 37 and 40 at the breakout box. If all resistances are not greater than 10K ohms, repair CID circuit to GROUND or POWER. Remove breakout box, reconnect all components and rerun QUICK TEST. If all resistances are greater than 10K ohms, remove breakout box, reconnect all components and diagnose TFI or DIS system.
12. Continuous Memory Codes 45, 46 or 48: Check Continuity of Coil Circuits From DIS to Coil Pack. Codes 45, 46 and 48 indicate a fault has been detected by the ECA in one of the 3 coils contained in the ignition pack. Possible causes for this fault are: an open in coil circuit from DIS module to coil pack or short to coil circuit GROUND or POWER in DIS module.
    NOTE: Codes 45, 46 and 48 refer to faults related to coils No. 3, 1, or 2 respectively. Coil No. 1 provides voltage to cylinders No. 3 and 4 spark plugs. Coil No. 2 provides voltage to cylinders No. 2 and 6 spark plugs. Coil No. 3 provides voltage to cylinders No. 1 and 5 spark plugs. The IDM input contains a pulse signal for each operating coil. If that coil fails, the corresponding pulse will be missing from the IDM input pulse signal.

    Turn key off and wait 10 seconds. Disconnect DIS module and set DVOM on 200-ohm scale. Measure resistance as described for appropriate service code:

    • Code 45: Measure resistance between pin No. 8 at the DIS module and coil pin No. 3 at coil pack.
    • Code 46: Measure resistance between pin No. 11 at the DIS module and coil pin No. 1 at coil pack.
    • Code 48: Measure resistance between pin No. 9 at the DIS module and coil pin No. 2 at coil pack.

    If all resistances are less than 5 ohms, go to next step. If resistances are greater than 5 ohms, repair open circuit and reconnect all components. Rerun QUICK TEST.

13. Checking Coil Pack For Shorts to Ground and Power. With key off, disconnect coil pack and DIS module connector (pins No. 7-12). Set DVOM on 200K-ohm scale. Measure resistance between pin No. 7 and pins No. 8, 9 and 11 at the DIS module connector. Measure resistance between pin No. 1 and pins No. 8, 9 and 11 at the DIS module connector. If all resistances are greater than 10K ohms, diagnose DIS ignition system. If all resistances are not greater than 10K ohms, repair short circuit, reconnect all components, and rerun QUICK TEST.
14. Continuous Memory Code 88: Check Continuity of DPI Circuit. Code 88 indicates an open in the Dual Plug Inhibit (DPI) circuit or an open or short to ground in coil No. 4. Possible causes for this fault are: open or short circuit in harness, Faulty ECA or DIS module or faulty coil No. 4. Turn key off and wait 10 seconds. Disconnect DIS connector (pins No. 7-12). Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion or loose wires. If connector is damaged, repair as necessary. Install breakout box and leave ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between pin No. 6 at the DIS vehicle harness connector and test pin No. 32 at the breakout box. If resistance is less than 5 ohms, remove breakout box, reconnect all components. Diagnose DIS ignition system. If system is okay, replace ECA. If resistance is not less than 5 ohms, repair open circuit, remove breakout box, reconnect all components and rerun QUICK TEST.
15. Symptom: Hard Start, Check DPI Circuit For Short to Ground. Turn key off and wait 10 seconds. Disconnect DIS connector (pins No. 7-12). Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion or loose wires. If connector is damaged, repair as necessary. Install breakout box and leave ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 32 and test pins No. 40 and 60 at the breakout box. If resistance is greater than 100K ohms, go to next step. If resistance is less than 100K ohms, repair short circuit, remove breakout box, reconnect all components and rerun QUICK TEST.
16. Check ECA For Short to Ground. Turn key off and wait 10 seconds. Disconnect DIS connector (pins No. 7-12). Install breakout box and connect ECA. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 32 and test pins No. 40 and 60 at the breakout box. If resistance is greater than 500 ohms, remove breakout box, reconnect all components. Diagnose DIS ignition system. If resistance is less than 500 ohms, replace ECA, remove breakout box, reconnect all components and rerun QUICK TEST.