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HOMESERVICE MANUALSPONTIAC1987GRAND PRIX BROUGHAM, 5.0 HREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSIS3.8L FEEDBACK CARBURETOR "C" CHARTSCHART C2A - IDLE SPEED CONTROL (ISC) (3.8L)
1987 Pontiac Grand Prix Brougham, 5.0 H

Chart C2A - Idle Speed Control (ISC) (3.8L)

1987 Pontiac Grand Prix Brougham, 5.0 HSECTION Chart C2A - Idle Speed Control (ISC) (3.8L)
NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).
  1. This is a functional test for ECM to cycle ISC plunger in and out smoothly, by grounding the ALCL test terminal.
  2. This is a functional test for ISC plunger switch. Light should go on when plunger is depressed.
  3. This tests for an open in circuit 427 to ISC. Low or no voltage indicates an open to the ECM, faulty ECM or poor ground. Voltage reading should be about battery voltage.
  4. This test manually applies voltage to ISC motor to determine if motor is defective.
  5. This tests for faulty Park/Neutral switch circuit 434. In Park or Neutral, voltage is normally low. In forward gear ranges, voltage should be about battery voltage.
Fig 1: Chart C2A - Idle Speed Control (ISC) Flow Chart (3.8L)
G4670
RENDER: 1.0x

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