Code 44 - THERMACTOR System

1) Warm engine to normal operating temperature. Upper radiator hose should be hot and pressurized. Turn engine off. Restart and run engine at curb idle and immediately initiate FUNCTION TESTS within 10 seconds and record codes. If any other codes are displayed, go to appropriate tests. If Code 11 is displayed, continue with FUNCTION TESTS. If Code 44 is displayed, go to next step.

2) Remove vacuum hose from TAB valve and connect vacuum gauge to hose. See Fig 1 . Start and run engine above 2000 RPM for 2 minutes. Stop engine, restart it and initiate FUNCTION TESTS. Observe vacuum gauge. If vacuum is always above 5 in. Hg, go to step 4. If vacuum is always below 5 in. Hg, go to step 6. If vacuum pulses above and below 5 in. Hg, go to next step.

Fig 1: Positive Thermactor Dump System

Courtesy of FORD MOTOR CO.

3) Reconnect hose to TAB valve. Remove vacuum hose from TAD valve and connect vacuum gauge to hose. Start and run engine above 2000 RPM for 2 minutes. Stop engine, restart it and initiate FUNCTION TESTS. Observe vacuum gauge. If vacuum pulses above and below 5 in. Hg, check and/or service thermactor air system. If vacuum is always above 5 in. Hg, go to step 8. If vacuum is always below 5 in. Hg, go to step 10.

4) With key off, disconnect MCU connector and TAB connector. Measure resistance between MCU connector pin No. 11 (White/Red wire) and ground. See Fig 2 . If reading is less than 1 k/ohm, repair short to ground. If reading is greater than 1 k/ohm, go to next step.

Fig 2: Thermactor System Test Connections

Courtesy of FORD MOTOR CO.

5) Measure TAB solenoid resistance. If reading is not within 50-110 ohms, replace TAB solenoid and retest. If Code 44 is still displayed, replace MCU. If resistance is correct, go to next step.

6) Check vacuum hose between TAB valve and TAB solenoid for damage. Repair as necessary. Check TAB solenoid output to ensure vacuum not present when engine is idling and solenoid is energized. If vacuum is present, go to next step. If vacuum is not present, replace solenoid.

7) Check TAB solenoid output to ensure vacuum is present when solenoid is energized (engine idling, 12 volts applied). If no vacuum is present, replace TAB solenoid. If vacuum is not present, go to next step.

8) With key off, disconnect MCU connector and TAD solenoid connector. Measure resistance between MCU connector pin No. 10 and ground. See Figure . If reading is less than 1 k/ohm, repair short to ground. If reading is greater than 1 k/ohm, go to next step.

9) Check TAD solenoid output to make sure vacuum is not present when solenoid is de-energized. Disconnect TAD solenoid from vehicle harness. Start and run engine at idle. If vacuum is present, replace TAD solenoid. If vacuum is not present, replace MCU.

10) Turn key off. Check vacuum hose between TAD valve and TAD solenoid for blockage or leaks. If hose is damaged, repair as necessary. If hose is okay, go to next step.

11) Remove TAD solenoid connector. Measure TAD solenoid resistance. If resistance is not within 50-110 ohms, replace solenoid. If resistance is within 50-110 ohms, go to next step.

12) Check TAD solenoid output to make sure vacuum is present when solenoid is energized. Install a jumper wire from TAD solenoid circuit No. 200 (White/Black wire) to ground. Start and run engine at idle. If vacuum is not present, replace solenoid. If vacuum is present, go to next step.

13) Turn key off. Measure resistance between TAD solenoid and MCU (circuit No. 687 Gray/Yellow, and circuit No. 200 Brown or Black/White). If reading is more than 5 ohms, repair circuit. If reading is 5 ohms or less, replace MCU.