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Code 44 - THERMACTOR System

  1. Check for manifold vacuum at input to TAB-TAD solenoids. If vacuum is present, go to next step. If not, check hose condition and routing.
  2. Remove vacuum hose from TAB valve and connect vacuum gauge to hose. Start engine and run at 2000 RPM for 2 minutes. Stop engine, then immediately restart and allow to idle. Begin Functional Test and watch vacuum gauge. If pulses are above and below 5 in. Hg, go to next step. If gauge is always above 5 in. Hg, go to step 4). If always below 5 in. Hg, go to step 6).
  3. Reconnect hose to TAB valve. Remove hose from TAB valve and connect vacuum gauge to hose. Start engine, run for 2 minutes above 2000 RPM, then stop engine. Restart immediately and observe vacuum gauge as Self-Test starts. If vacuum pulses above and below 5 in. Hg, check Thermactor pump operation. If vacuum is always above 5 in. Hg, go to step 10). If below 5 in. Hg, go to step 12).
  4. Disconnect MCU connector and TAB connector. Measure resistance between MCU connector pin 11 and ground. If less than 1000 ohms, repair short to ground. If greater than 1000 ohms, go to next step.
  5. Check at TAB solenoid output to make sure vacuum is not present when solenoid is deactivated (engine idling, harness disconnected). If vacuum is present, replace TAB solenoid. If no vacuum, replace MCU module.
  6. Check vacuum hose between TAB valve and TAB solenoid for damage. If damaged, repair or replace. If hose is okay, go to next step.
  7. Measure TAB solenoid resistance. If not within 50-110 ohms, replace solenoid. If resistance is correct, go to step 8).
  8. Check at TAB solenoid output to be sure vacuum is present when solenoid is activated (engine idling, 12 volts applied). If no vacuum, replace TAB solenoid. If vacuum is present, go to next step.
  9. Disconnect MCU connector and TAB solenoid connector. Continuity should exist between MCU pin 11 and Wht/Red wire at connector, and between pin 20 and Gry/Yel wire at connector. If resistance is more than 5 ohms, repair circuit. If less than 5 ohms, replace MCU module.
  10. Disconnect MCU connector and TAD solenoid connector. Measure resistance between MCU pin 10 and ground. If resistance is less than 1000 ohms, repair short. If more than 1000 ohms, go to next step.
  11. Check at TAD solenoid output to ensure vacuum is not present with engine idling and TAD solenoid connector disconnected. If vacuum is present, replace TAD solenoid. If no vacuum, replace MCU module.
  12. Check vacuum hose between TAD valve and TAD solenoid for blocks or leaks. If problems are found, repair. If hose is okay, go to next step.
  13. Remove TAD solenoid connector and measure resistance across TAD solenoid. If not between 50-110 ohms, replace solenoid. If resistance is between 50-110 ohms, go to next step.
  14. Check at TAD solenoid output to ensure vacuum is present with engine idling and solenoid energized with 12 volts. If vacuum is present, go to next step. If not, replace solenoid.
  15. Measure resistance of Wht/Blk wire between MCU pin 10 and TAD connector, then resistance of Gry/Yel wire between pin 20 and TAD connector. If resistance in either circuit is more than 5 ohms, repair circuit. If less than 5 ohms, replace MCU module.
Fig 1: Thermactor System Test Connections
G208
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