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DTC P1664 - 1-4 SKIPSHIFT LIGHT CONTROL CIRCUIT Pontiac Firebird IV

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

Circuit Description

Ignition voltage is supplied directly to 2nd and 3rd gear blockout light. PCM controls light by grounding control circuit through an internal switch called a driver. Primary function of driver is to supply ground for component being controlled. Each driver has a fault line which is monitored by PCM. When PCM is commanding a component on, voltage on control circuit should be low (near zero). When PCM is commanding a component off, voltage of circuit should be high (near battery voltage). If fault detection circuit senses a voltage other that what is expected, fault line will change, causing DTC to set.

DTC will set when following conditions are present

  1. Engine speed more than 600 RPM.
  2. PCM detects commanded state of driver and actual state do not match.
  3. Conditions met for 5 seconds.