How To Use Circuit Tests
- Ensure all non-EEC-IV related faults found while performing steps in BASIC TESTING article in this section have been corrected. Follow each test step in order until fault is found. When more than one code is retrieved, start with first code displayed.
- CIRCUIT TESTS ensure electrical circuits are okay before sensors or other components are replaced. Always test circuits for continuity between sensor and PCM. Test all circuits for short to power, opens or short to ground. Voltage Reference (VREF) and Voltage Power (VPWR) circuits should be tested with ignition on unless otherwise specified in CIRCUIT TESTS.
- DO NOT measure voltage or resistance at PCM. DO NOT connect any test light unless specified in testing procedure. All measurements are made by probing rear of connector. Isolate both ends of a circuit and turn ignition off when checking continuity.
- Disconnect solenoids and switches from harness before measuring continuity and resistance or applying voltage. After each repair, reconnect all component connections and repeat QUICK TEST.
- An open circuit is defined as a resistance reading of greater than 5 ohms. This specification tolerance may be too high for some items in EEC-IV system. If resistance approaches 5 ohms, always clean suspect connector and coat it with protective dielectric silicone grease. A short is defined as a resistance reading of less than 10,000 ohms to ground, unless stated otherwise in CIRCUIT TEST.
NOTE:
In following tests, circuit diagrams and illustrations are courtesy of Ford Motor Co.
CIRCUIT TESTS are grouped as follows.
- A-C - No Start & Voltage Tests
- DA-DS - Input Sensor Tests
- FD-FF - Additional Input Component Tests
- G-J - Fuel Control System Tests
- KA-TG - PCM Output Tests
CIRCUIT TEST INDEX
| Circuit Test Title | Circuit Tested | |
|---|---|---|
| No-Start & Voltage Tests | ||
| AA | No Start (Distributor Ignition System) | |
| AB | No Start (2.3L) | |
| AC | No Start (4.0L) | |
| B | Vehicle Battery | |
| C | Reference Voltage | |
| Input Sensor Tests | ||
| DA | IAT/ECT Sensor | |
| DC | MAF Sensor | |
| DF | MAP/BARO Sensor | |
| DG | Knock Sensor | |
| DH | Throttle Position Sensor | |
| DJ | Engine RPM Sensor | |
| DL | DPFE Sensor & EVR Solenoid | |
| DN | EVP Sensor & EVR Solenoid | |
| DP | Vehicle Speed Sensor | |
| DR | Cylinder Identification Circuit | |
| DS | Programmable Speedometer/Odometer Module | |
| Additional Input Component Tests | ||
| FD | Brake On-Off (BOO) Switch | |
| FE | Electrical Load Inputs | |
| FF | Power Steering Pressure Switch | |
| Fuel Control System Tests | ||
| G | MAF/TPS Fuel Injector Pulse Width Test | |
| H | Fuel Control | |
| HA | Adaptive Fuel | |
| J | Fuel Pump Circuit | |
| PCM (Processor) Output Tests | ||
| KA | EVR Solenoid | |
| KB | CANP Valve | |
| KC | Secondary Air Injection Solenoid | |
| KD | Canister Purge Solenoid | |
| KE | Idle Air Control Solenoid | |
| KM | WAC & A/C Demand Switch | |
| KP | Octane Adjust | |
| M | Dynamic Response Test | |
| ML | STO/MIL | |
| NA | IDM (Distributor Ignition System) | |
| NB | IDM (2.3L) | |
| NC | IDM (4.0L) | |
| PA | Spark Timing Check (Distributor Ignition System) | |
| PB | Spark Timing Check (2.3L) | |
| PC | Spark Timing Check (4.0L) | |
| QA | No Codes/Codes Not Listed | |
| QB | Continuous Memory Service Code 15 Or 512 | |
| QC | Output State Check Not Functioning | |
| S | System Check | |
| TA | CPP/PNP Switch | |
| TB | 4x4 Low/Transmission Control Switch | |
| TC | Transmission Solenoids | |
| TD | Manual Lever Position Sensor | |
| TE | Transmission Oil Temperature Sensor | |
| TF | Transmission Speed Sensor | |
| TG | Electronic Transmission Continuous Memory Service Codes | |