Firebird V8-305 5.0L (1982)
Idle/Throttle Speed Control Unit: Testing and Inspection
Fig. 031 - Chart C-2A Idle Speed Control (ISC) Check.
1. ECM functional test--ECM should cycle ISC in both directions when the test terminal is grounded.
2. ISC plunger functional test--light should go ON when plunger is depressed.
3. Voltage should be near battery voltage.
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Checks for open in circuit to ISC.
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Low or no voltage indicates an open to the ECM, faulty ECM or poor ground.
4. Manually applies voltage to the ISC motor to determine if fault is in motor.
5. Checks for faulty P/N switch circuit.
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In park or neutral, voltage is normally low.
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In drive ranges voltage goes to near battery voltage.
