Skyhawk L4-121 2.0L VIN P TBI (1984)
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Throttle position sensor output not changing, indicating a steady road speed.
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Transmission 3rd gear switch closed.
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Brake switch closed.
1.
Light "OFF" confirms transmission 3rd gear switch is open.
2.
At 30 mph, the third gear switch should close. Test light will come "ON" and confirm battery supply and closed brake switch.
3.
Grounding the diagnostic terminal with engine "OFF" should energize the TCC solenoid. This test checks the capability of the ECM to control the
solenoid.
4.
Solenoids are turned "ON" or "OFF" by the ECM internal electronic switches called "drivers". Each driver is part of a group of four called
"Quad-Drivers". Failure of one can damaged any other driver within the set.
Solenoid coil resistance must measure more than 20 ohms. Less resistance will cause early failure of the ECM "DRIVER". Using on ohmmeter, check
the solenoid coil resistance of the following before installing a replacement ECM.
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Pulsair solenoid.
Check TCC solenoid resistance as follows:
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Disconnect TCC at transmission.
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Connect ohmmeter between transmission connector opposite harness connector Terminal "A" and "D".
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Raise drive wheels.
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Run engine in drive about 30 M.P.H. to close third gear apply switch.
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Replace the TCC solenoid and ECM if resistance measures less than 20 ohms when switch is closed.
