Spark Knock Test (V8)
- If vehicle is not equipped with knock sensor or 3-connector ignition module, check ignition timing and reset as necessary. Testing is now complete. MCU system is functional and problem must be in some other area.
- If vehicle is equipped with knock sensor or 3-connector module, disconnect knock sensor and set timing. Disconnect 2-wire connector (Yellow and Black/White wires) and jumper wires together at module.
- Check ignition timing. If timing retards 16-20°, reconnect module and go to next step. If timing does not retard, replace module and repeat Spark Knock Test.
- With vehicle at normal operating temperature, set fast idle screw on cam step that will maintain engine speed above 1200 RPM. Read and record ignition timing.
- Locate zone vacuum switch, then remove and plug hose from it. Recheck timing, If timing retards more than 5 degrees and system has a knock sensor, go to step 7. If no knock sensor, testing is complete, MCU system okay. If timing does not retard 5 degrees, go to next step.
- While engine is still at 1 200 RPM, disconnect 2-wire connector at ignition module. If timing retards, check Yellow wire for short to ground. If okay, replace MCU module and retest. If timing does not retard, check Yellow wire for open circuit. If okay, replace MCU module and retest.
- Reconnect knock sensor. Repeat MCU Running Test, but do not simulate knock by tapping rod on intake manifold. If service code 25 is obtained, MCU system is okay. If any other code is observed, replace knock sensor and retest.
| FORD MCU SYSTEM SERVICE CODES & SUB-ROUTINE TESTS | |||
|---|---|---|---|
| Code | 4-Cylinder Test | 6-Cylinder Test | V8 Test |
| None | 14 Functional Test Not Operating | 14 Functional Test Not Operating | 29 No Self-Test Output |
| No Start | 1 No Start Test | 1 No Start Test | 18 No Start Test |
| 11 | System OK | System OK | System OK |
| 12 | ..... | ..... | 24 Idle Speed Incorrect |
| 25 | ..... | ..... | 28 Knock Detection System |
| 33 | 13 Running Test Not Initiated | 13 Running Test Not Initiated | ..... |
| 41 | 6 Fuel Always Lean | 8 Fuel Always Lean | 22 Fuel Always Lean |
| 42 | 7 Fuel Always Rich | 9 Fuel Always Rich | 23 Fuel Always Rich |
| 44 | 10 Thermactor System | 10 Thermactor System | 25 Thermactor System |
| 45 | 11 Thermactor Air Diverter | 11 Thermactor Air Diverter | 26 Thermactor Air Diverter |
| 46 | 12 Thermactor Air By-Pass | 12 Thermactor Air By-Pass | 27 Thermactor Air By-Pass |
| 51 | 2 Low Temperature Switch | 5 Low Temperature Vacuum Switch | 20 Vacuum Switch Open |
| 52 | 3 Idle Tracking Switch | 4 Vacuum Switch | ..... |
| 53 | 4 Vacuum Switch | 4 Vacuum Switch | 19 Electrical Temp. Switch Open |
| 54 | ..... | ..... | 19 Electrical Temp. Switch Open |
| 55 | ..... | ..... | 20 Vacuum Switch Open |
| 56 | ..... | 4 Vacuum Switch | ..... |
| 61 | ..... | ..... | 21 Vacuum Switch Closed |
| 62 | 3 Idle Tracking Switch | 4 Vacuum Switch | Baro |
| 63 | 4 Vacuum Switch | 4 Vacuum Switch | ..... |
| 65 | ..... | ..... | 21 Vacuum Switch Closed |
| 66 | ..... | 4 Vacuum Switch | ..... |