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Home >> Ford >> 1993 >> Probe Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 2.0L M/T >> Circuit Tests >> Circuit Test NA - Distributor Ignition System Ignition Diagnostic Monitor (IDM) >> Diagnostic Aids

Diagnostic Aids

The IDM is an input signal to the PCM that verifies spark plug fire based on ignition coil primary discharge. IDM signal consists of a single pulse for each engine RPM. No IDM pulse indicates secondary ignition misfire.

Perform this test when directed by QUICK TEST. This test is only intended to diagnose EEC-IV portion of ignition system. For additional information on ignition system and component testing, see SYSTEM/COMPONENT TESTS - EEC-IV article in this section. To prevent replacing good components, be aware the following non-EEC related areas may be cause of problem:

This test is intended to diagnose:

Fig 1: IDM Circuit Schematic
G93E40760
TEST PIN NO. 4 (IDM) WIRE COLOR I.D.

Application Wire Color
2.0L Red/Black
TEST PIN NO. 36 (SPOUT) WIRE COLOR I.D.

Application Wire Color
2.0L Red/Blue

1) Continuous Memory Code 14/211  Code 14/211 indicates 2 successive erratic Profile Ignition Pick-Up (PIP) pulses occurred, resulting in a possible engine miss or stall. Check for the following possible causes of fault:

Repair if necessary. Clear code, and repeat QUICK TEST. If problem is not found, go to step 2). If vehicle does not start, go to CIRCUIT TEST AA.

2) Continuous Memory Code 18/212: Check IDM Circuit Continuity  Continuous Memory Code 18/212 indicates loss of IDM input to PCM. Possible causes for this fault are:

If vehicle is a no-start, go to CIRCUIT TEST AA. If vehicle starts, go to step 4).

3) Check IDM Circuit Continuity (Non-CCD)  Turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Disconnect ICM. Measure resistance between test pin No. 4 at breakout box and IDM terminal at ICM wiring harness connector. If resistance is 5 ohms or less, go to step 5). If resistance is more than 5 ohms, repair open circuit, and repeat QUICK TEST.

4) Check IDM Circuit Continuity (CCD)  Turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Disconnect ignition coil and ICM. Measure resistance between test pin No. 4 at breakout box and IDM terminal at ICM wiring harness connector. If resistance is not 20,000-24,000 ohms, repair open circuit and repeat QUICK TEST. If resistance is 20,000-24,000 ohms, go to step 5).

5) Check IDM Circuit For Short To Power (Except VREF)  Turn ignition off. Leave ICM and PCM disconnected. Measure voltage between breakout box test pin No. 4 and negative battery terminal. Turn ignition on. Measure voltage between test pin No. 4 and test pins No. 40 and 60 at breakout box. If voltage is more than 10.5 volts, repair short circuit. Clear codes, and repeat QUICK TEST. If voltage is 10.5 volts or less, go to step 6).

6) Check IDM Circuit For Short To PIP & VREF  Turn ignition off. Leave PCM and ICM disconnected. Remove scan tool (if applicable). For shorts to PIP, measure resistance between test pins No. 4 and No. 56 at break-out box. For shorts to VREF, measure resistance between test pinNo. 4 and test pins No. 20, 40, 46 and 60 at breakout box. If each resistance is 10,000 ohms or less, repair short circuit and repeat QUICK TEST. If each resistance is more than 10,000 ohms, go to step 7).

7) Check IDM Circuit For Short To Ground  Turn ignition off. Leave ignition coil, ICM and PCM disconnected. Measure resistance between test pin No. 4 and test pins No. 20, 40, 46 and 60 at breakout box. If each resistance is more than 10,000 ohms, go to step 8). If any resistance is 10,000 ohms or less, repair short to ground in IDM, SIG RTN, or PWR GND circuit. Clear codes, and repeat QUICK TEST.

8) Check ICM  Turn ignition off. Connect PCM to breakout box. Reconnect ICM and ignition coil to wiring harness connectors. Connect DVOM between test pins No. 4 and 16 at breakout box. Start engine. Observe DVOM for voltage surge while lightly tapping on ICM and Camshaft Position (CMP) sensor to simulate road shock. Wiggle all ICM and CMP sensor wiring and harness connectors. If fault (voltage surge) is indicated, disconnect and inspect wiring harness connectors and terminals for damage. If fault (voltage surge) is indicated, go to step 9). If connectors and terminals are okay, check ignition system. See SYSTEM/COMPONENT TESTS - EEC-IV article in this section.

9) Check PCM & Harness Connectors  Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. If connector is damaged, repair as necessary. Clear codes, and repeat QUICK TEST. If connector is okay, go to step 10).

10) Check PCM For Short To Power  Turn ignition off. Connect PCM to breakout box. Disconnect the following sensors as applicable.

Disconnect ICM wiring harness connector. Measure voltage between test pin No. 4 at breakout box and chassis ground. Turn ignition on. Measure voltage between test pin No. 4 and test pins No. 40 and 60 at breakout box. If either voltage reading is more than 10.5 volts, replace PCM and repeat QUICK TEST. If both voltage readings are 10.5 volts or less, go to step 11).

11) Check PCM For Short To Ground  Turn ignition off. Leave PCM connected to breakout box. Disconnect ICM and CMP. Measure resistance between test pin No. 4 and test pins No. 40, 46 and 60 at breakout box. If resistance is more than 10,000 ohms, check ignition system. See SYSTEM/COMPONENT TESTS - EEC-IV article in this section. If resistance is 10,000 ohms or less, replace PCM and repeat QUICK TEST.

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