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 1200 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 11 1 No Start Test System OK 1 No Start Test System OK 18 No Start Test 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 ..... 63 4 Vacuum Switch 4 Vacuum Switch ..... 65 ..... ..... 21 Vacuum Switch Closed 66 ..... 4 Vacuum Switch .....