Factory service information has a diagnostic procedure for thing's to check . Hooking up a factory scan tool (tech2) would be the first step ,Checking for DTC'S - diagnostic trouble code's
DTC P1661 Malfunction Indicator Lamp (MIL) Control Circuit
A voltage is supplied directly to the malfunction indicator lamp (MIL). The powertrain control module (PCM) controls the lamp by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the PCM. When the PCM is commanding a component ON, the voltage of the control circuit should be near 0 volts. When the PCM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be near battery voltage. If the fault detection circuit senses a voltage other than what is expected, the fault line status will change causing the DTC to set.
Perform the Powertrain On-Board Diagnostic System Check first, when the following conditions are present:
• When the MIL does not turn ON when the the ignition switch is turned to the RUN position
Malfunction Indicator Lamp (MIL) Inoperative
Circuit Description
There should be a steady MIL with the ignition ON and the engine not running. Ignition feed voltage is supplied directly to the MIL bulb. The Powertrain Control Module (PCM) turns the MIL ON by grounding the MIL control circuit. No MIL with the key ON, engine not running and DTC P1641 set suggests an open in the MIL control circuit.
The diagnostic procedure for this is 17 step's . , the basic thing's checking B+ voltage at the connector for the IPC , checking the control circuit at the PCM connector , using the scan tool to check for bidirectional control of the MIL lamp . Checking wiring circuit for the control circuit . Disconnect the PCM connector that has control side wire for the MIL an ground it an see if the light lights . If it does ,replace the PCM . Check for open wire . ETC........
Check the MIL control circuit for an open.
If the MIL control circuit is open, repair as necessary. Refer to Wiring Repairs .
Finding wire diagrams would be a big help to you .
SOURCE: I have a 1997 Camaro
check to see if the computer is grounding that circuit for the bulb check when the key is turned on. you should have battery voltgage to the light and the computer grounds the circuit for 2 seconds when key is turn to run position.
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