Idle Speed Control System Ford Cab & Chassis Ranger

DESCRIPTION

The purpose of the Idle Speed Control (ISC-E) system, used on the 2.0L Ranger, is to control engine RPM by means of a DC motor throttle actuator. It does not control any other engine function.

Scheme 66

1. Start and run engine to stable idle. Upper radiator hose should be hot and pressurized. Carburetor should be off high cam.
2. Turn ignition off. Connect a jumper wire from Self-Test Input (STI) to Pin 2. (Scheme 66) (Scheme 66): Meter Hook-Up for Reading Codes
3. Set analog VOM on a DC voltage range to read from 0 to 15 volts DC. Connect VOM from battery positive post to Pin 4 Self-Test Output (STO) in the Self-Test Connector.
4. Start and run engine to stable idle. Upper radiator hose should be hot and pressurized. Carburetor should be off high cam. Activate self-test.
5. Observe and record all service codes. Service codes are transmitted to the Self-Test Output terminal in the form of timed pulses. On the analog meter each pulse equals 1 meter sweep. One-half second on-time pulse for each digit. Two seconds off-time between digits. Four seconds off-time between codes. Eight to twelve seconds before fast and service codes.

Example: 6 pulses (sweeps) equals digit 6; two second pause then 8 pulses (sweeps) equals digit 8, this will equal code 68.

SERVICE CODES

TEST 1

1. Turn ignition off. Disconnect self-test jumper. Connect tachometer and start engine. Read engine RPM. Engine RPM should be 775 to 825. If reading in correct go to next step. If not, go to step 3).
2. Turn ignition off. Disconnect engine coolant temperature switch. Start engine. Engine RPM should be 1175 to 1225. If reading is correct, ICS system is working properly, go to TEST 6. If not, go to next step.
3. Engine Preparation Run vehicle for 2 minutes at 2000 RPM. Verify water temperature was above 128°F (53°C) during self-test (upper radiator hose hot and pressurized). If reading is correct go to next step. If not, repair engine cooling system.
4. ECT Switch Check Disconnect vehicle harness from Engine Coolant Temperature (ECT) switch. Check contacts of ECT switch. Contact should be closed above 128°F (53°C). Measure resistance. If resistance is 5 ohms or less go to next step. If resistance is more than 5 ohms, replace ECT switch and retest.
5. Continuity Check Disconnect vehicle harness from the ISC-E processor. Check circuits 354 and 60 for continuity. Measure resistance. If resistance is 5 ohms or less go to next step. If resistance is more than 5 ohms, service or replace circuit and retest.
6. Short to Ground Connect one lead of VOM to circuit 354 and the other to engine ground. Measure resistance. If resistance is more than 1000 ohms, replace ISC-E processor and retest. If resistance is 1000 ohms or less, repair or replace circuit.

Scheme 67

Scheme 68

1. Turn ignition off. Disconnect processor. Set VOM on 200 ohm scale. Measure resistance of the Idle Tracking Switch (ITS) between processor connector Pin 7 and processor connector Pin 24. Move throttle lever off the DC motor shaft. Resistance reading should be less than 5 ohms. Release the throttle lever to contact the DC motor shaft. If throttle does not contact shaft, depress shaft. Resistance reading should be greater than 5 ohms. If readings are correct go to step 3). If not, go to next step.
2. ITS Check Ignition off. VOM on 200 ohm scale. Disconnect DC motor connector. Measure resistance of ITS from DC motor connector. Lift and release throttle lever. Resistance reading should be less than 5 ohms with the throttle lever lifted. Resistance should be greater than 5 ohms with the throttle contacting the DC motor shaft. If throttle does not contact shaft, depress shaft. If readings are correct service open in harness from DC motor connector to processor connector and repeat quick test. If not, replace DC motor and repeat quick test. (Scheme 67): DC Motor Connector
3. DC Motor Movement Reconnect processor. Start engine an perform quick test. Check for motion of DC motor shaft during quick test. If motor shaft moves during test, replace processor and repeat quick test. If not, go to next step.
4. Continuity Check Disconnect processor. Set VOM on 200 ohm scale. Measure continuity of harness from motor connector to processor connector. If resistance is 5 ohms or less for each, go to next step. If not, service harness and repeat quick test. (Scheme 68): Processor Circuit
5. DC Motor Movement Turn ignition off. Disconnect DC motor connector. Connect insulated clip leads from the battery terminals to the DC motor connector pins.

ITS Terminals. Scheme 69

Apply voltage across the 2 upper pins and observe motor shaft movement. Reverse polarity across the two upper pins and observe motor shaft reverse movement. If motor moves in both directions, replace processor and repeat quick test. If not, replace DC motor and repeat quick test.

TEST 3: CODE 68

1. Disconnect ISC-E processor connector. Set VOM on 200 ohm scale. Measure resistance of ITS between connector Pin 7 and connector Pin 24 with throttle held open. Resistance should be less than 5 ohms when the ISC motor shaft is depressed. If reading is correct, go to step 3). If not, go to next step.
2. ITS Operation. Disconnect ISC motor from harness. Set VOM on 200 ohm scale. Measure resistance of ITS at motor connector (Yellow and Purple wires) with throttle held open. Resistance should be less than 5 ohms and change to greater than 5 ohms when the ISC motor shaft is depressed. If reading is correct, service harness and repeat quick test. If not, replace motor and repeat quick test.
3. Mechanical Idle Adjustment. Perform mechanical idle speed adjustment. Return to this step after adjustment. Rerun quick test. If code 68, replace ISC-E processor and repeat quick test. If code 11, system is OK.

Verifying DC Motor Movement

Bring vehicle to operating temperature. Initialize self-test. Visually verify DC motor movement during self-test. If there is movement, go to Test 2 step 4). If not, set idle adjustment.

Scheme 70

1. Continuity Check (STI) Disconnect positive battery cable. Disconnect ISC-E processor. Set VOM on 200 ohm scale. Measure resistance between processor connector Pin 16 and Self-Test Input (STI) connector. Resistance should be less than 5 ohms. If resistance is less than 5 ohms, go to next step. If not, service harness and repeat quick test.
2. Continuity Check (STO) Set VOM on 200 ohm scale. Measure resistance between processor connector Pin 18 and Self-Test Output (STO) connector. Resistance should be less than 5 ohms. If resistance is less than 5 ohms, go to next step. If not, service harness and repeat quick test. (Scheme 70): Self Test Connector
3. Continuity Check (GROUND) Set VOM on 200 ohm scale. Measure resistance between negative battery cable and Self-Test ground connector. Resistance should be less than 5 ohms. If resistance is less than 5 ohms, go to next step. If not, service harness and repeat quick test.
4. Continuity Check (GROUND) Set VOM on 200 ohm scale. Measure resistance between negative battery cable and processor connector Pin 24. Resistance should be less than 5 ohms. If resistance is less than 5 ohms, go to next step. If not, service harness and repeat quick test.
5. Continuity Check (POWER) Set VOM on 200 ohm scale. Measure resistance between positive battery cable and processor connector Pin 1. Resistance should be less than 5 ohms. If resistance is less than 5 ohms, go to next step. If not, service harness and repeat quick test.
6. Continuity Check (IGNITION RUN) Set VOM on 200 ohm scale. Measure resistance from processor connector Pin 14 to ignition run circuit 687. Resistance should be less than 5 ohms. If resistance is less than 5 ohms, replace ISC-E processor and repeat quick test. If not, service harness and repeat quick test.

TEST 6: DIAGNOSTICS BY SYMPTOMS TEST

Note. Use these test procedures only if the drive complaint is high RPM at idle, low RPM at idle or erratic engine speeds.

If abnormal high or low RPM at idle, check vacuum hoes routing, see VACUUM DIAGRAMS article. Also check idle speed setting. See appropriate article in the TUNE-UP section. Minor idle fluctuations are normal due to load changes. See appropriate article in the TUNE-UP section.

Wiring Diagram (2.0L ISC-E). Scheme 71