Diagnostic Aids

WARNING: This page is about a different car, the 1995 Ford Pickup, 1995 Ford Econoline, 1995 Ford Club Wagon, and 1995 Ford Bronco. However, it is still accessible from the selected car via links, so may be relevant.

Enter this CIRCUIT TEST only when steps in QUICK TEST have been successfully completed but engine still does not start or if directed here from another test or chart.

This test is only intended to diagnose the following EEC-IV ignition systems and circuits:

Powertrain Control Module (PCM).
Spark (PCM-controlled).
Wiring harness circuits (PIP, SPOUT, IGN GND and VPWR).

TEST PIN NO. 16 (IGN GND) WIRE COLOR IDENTIFICATION

Application	Wire Color
All Models	Orange/Red

TEST PIN NO. 36 (SPOUT) WIRE COLOR IDENTIFICATION

Application	Wire Color
All Models	Pink

TEST PIN NO. 56 (PIP) WIRE COLOR IDENTIFICATION

Application	Wire Color
All Models	Gray/Orange

Fig 1: ICM Circuit & Connector Terminal ID (5.0L)

To prevent replacement of good components, be aware the following non-EEC related areas and components may be cause of problem:

Fuel quality and quantity.
Ignition (general system condition).
Engine mechanical components.
Starter and battery circuits.
Distributor.
Camshaft Position (CMP) sensor.
Ignition Control Module (ICM).
Ignition coil.

1) Check No-Start Condition

Try to start engine. If engine does not start, go to next step. If engine starts, no-start condition is intermittent. Check and repair ignition system as necessary. Proceed to appropriate SYSTEM/COMPONENT TESTS - EEC-IV (5.0L) article in the ENGINE PERFORMANCE section.

2) Attempt To Crank Engine

Try to crank engine. If engine does not crank, check vehicle starting and charging systems. If engine cranks, verify inertia switch button is pushed in. If inertia switch button is pushed in, go to next step.

3) Check VREF Signal At TP Sensor

Turn ignition off. Disconnect Throttle Position (TP) sensor. Turn ignition on (engine off). Measure voltage at TP sensor harness connector between VREF and SIG RTN. See Fig 2. If voltage is 4-6 volts, reconnect TP sensor and go to next step. If voltage is not 4-6 volts, go to CIRCUIT TEST C.

Fig 2: TP Sensor Wiring Harness Connector Terminal ID (5.0L)

4) Check For Spark At Plugs

Disconnect any spark plug wire. Connect spark tester between spark plug wire and ground. Crank engine and check for spark. If spark is present and consistent, connect spark plug wire and go to step 14). If spark does not exist, connect spark plug wire and go to step next step.

5) Check For Spark At Coil

Remove coil secondary wire from distributor. Install spark tester. Check for spark while cranking engine. If spark exists, connect coil wire, and service ignition secondary system. If no spark exists, connect coil wire and go to next step.

6) Check Ignition Circuit Ground Continuity

Turn ignition off. Disconnect and inspect PCM 60-pin connector. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Disconnect Camshaft Position (CMP) sensor connector. Measure resistance between test pin No. 16 at breakout box and IGN GND circuit of CMP sensor connector. If resistance is 5 ohms or more, repair open IGN GND circuit. Remove breakout box, reconnect components and repeat QUICK TEST. If resistance is less than 5 ohms, go to next step.

7) Isolate SPOUT Circuit Fault

Connect CMP sensor connector. Connect PCM to breakout box. Set breakout box timing switch to DIST position. Try to start vehicle. If vehicle starts, go to step 12). If vehicle does not start, go to next step.

8) Check SPOUT Signal

Turn ignition off. Set breakout box timing switch to DIST position. Set DVOM on 20-volt scale. Turn ignition on. Measure voltage between test pin No. 36 at breakout box and negative battery terminal while cranking engine. If voltage is 3-6 volts, EEC-IV system is not at fault. Diagnose ignition system. See IGNITION SYSTEMS in SYSTEM/COMPONENT TESTS - EEC-IV (5.0L) article in the ENGINE PERFORMANCE section. If voltage is not 3-6 volts, go to next step.

9) Check SPOUT & PIP Circuits For Short To Power

Turn ignition off. With breakout box installed, move timing switch to COMPUTED position. Disconnect PCM. Disconnect CMP sensor and ICM connectors. Turn ignition on. Measure voltage between test pin No. 36 (SPOUT) and negative battery terminal. Also, measure voltage between test pin No. 56 (PIP) and negative battery terminal. If either reading is more than 10.5 volts, repair short to power. Remove breakout box, reconnect components and repeat QUICK TEST. If both readings are 10.5 volts or less, go to next step.

10) Check SPOUT & PIP Circuits For Short To Ground

Turn ignition off. Measure resistance between test pin No. 36 (SPOUT) and test pins No. 16, 20, 40, 46 and 60 for short to ground. Also, measure resistance between test pin No. 36 and test pin No. 56 for short to PIP. Also, measure resistance between test pin No. 56 (PIP) and test pins No. 16, 20, 40, 46 and 60. If all readings are 10,000 ohms or more, go to next step. If any reading is less than 10,000 ohms, repair short in wiring harness. Remove breakout box, reconnect components and repeat QUICK TEST. If engine still does not start, go to next step.

11) Isolate Shorts In PCM

Turn ignition off. With breakout box installed, reconnect PCM. Disconnect CMP and ICM connectors. Measure resistance between test pin No. 36 (SPOUT) and test pins No. 37, 40, 57 and 60. Measure resistance between test pin No. 56 (PIP) and test pins No. 37, 40, 57 and 60. If any reading is less than 500 ohms, replace PCM. Remove breakout box, reconnect components and repeat QUICK TEST. If all readings are 500 ohms or more, reconnect components, and go to next step.

12) Check PIP Signal

Turn ignition off. With breakout box installed and PCM connected, move timing switch to COMPUTED position. While cranking engine, measure voltage between test pin No. 56 (PIP) and test pins No. 40 and 60. If voltage is 3-7 volts, replace PCM. Remove breakout box, reconnect components and repeat QUICK TEST. If voltage is not 3-7 volts, go to next step.

13) Check Continuity Of PIP Circuit

Turn ignition off. Disconnect PCM from breakout box. Disconnect CMP sensor and ICM connectors. Measure resistance between test pin No. 56 and PIP circuit of ICM or CMP sensor. If resistance is 5 ohms or more, repair open PIP circuit. Remove breakout box, reconnect components and repeat QUICK TEST. If resistance is less than 5 ohms, remove breakout box and diagnose ignition system. See IGNITION SYSTEM in SYSTEM/COMPONENT TESTS - EEC-IV (5.0L) article in the ENGINE PERFORMANCE section.

14) Verify SPOUT Signal

Turn ignition off. Disconnect PCM 60-pin connector, and inspect for damaged pins, corrosion and loose wires. Repair as necessary. Install breakout box, leaving PCM connected. Ensure breakout box timing switch is in COMPUTED position. Set DVOM on 20-volt scale. Measure voltage between test pin No. 36 and test pins No. 40 and 60 while cranking engine. If voltage is 3-6 volts, go to step 21). If voltage is not 3-6 volts, return to step 9).

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.

CAUTION: Use safety precautions when working on fuel system. DO NOT allow smoking or open flame. If fuel starts leaking, immediately turn ignition off.

21) Fuel Pump Check

Connect pressure gauge to vehicle. Note initial pressure reading. Pressurize fuel system by turning ignition on for one second, and observe pressure gauge. Turn ignition off, and wait 10 seconds. Repeat sequence 5 times. If pressure increases, go to CIRCUIT TEST S. If pressure does not increase, repair fuel system as necessary. See FUEL SYSTEM in BASIC TESTING - 5.0L article in the ENGINE PERFORMANCE section.