Additional Reference Information
Speed Control Servo Operation and FunctionPIN 1 - Motor Common: Hot in run or start. Load test circuit to ensure current carrying capability. Disconnect C122 then with the key in the run position, measure voltage from Pin 1 to ground, then re-measure with a test lamp (1156) from Pin 1 to ground. The difference between the two measurements should be less than 0.3 VDC. If the voltage drop test fails, check the speed control system related terminals at the PCM connector to make sure they are not spread too far. If the terminals are okay, check the wiring.
PIN 2 - Motor Phase C: The PCM completes the circuit to ground as each motor phase is sequentially fired. This circuit carries the same current as the motor common. It is important to load test this circuit without back feeding the PCM or risk damaging the internals. With the key off, remove C122 and PCM connectors and conduct a voltage drop test on the Pin 2 circuit. Apply B+ (with a fused jumper) to the terminal on the servo end of the harness and with a DVOM set to DC Volts record the voltage at the PCM terminal to ground. Next re-measure voltage while a test lamp is connected from the PCM terminal to ground. The difference between the two measurements should be less than 0.3 VDC, otherwise check the wiring.
PIN 3 - Motor Phase B: The PCM completes the circuit to ground as each motor phase is sequentially fired. This circuit carries the same current as the motor common. It is important to load test this circuit without back feeding the PCM or risk damaging the internals. With the key off, remove C122 and PCM connectors and conduct a voltage drop test on the Pin 3 circuit. Apply B+ (with a fused jumper) to the terminal on the servo end of the harness and with a DVOM set to DC Volts record the voltage at the PCM terminal to ground. Next re-measure voltage while a test lamp is connected from the PCM terminal to ground. The difference between the two measurements should be less than 0.3 VDC, otherwise check the wiring.
PIN 4 - Motor Phase A: The PCM completes the circuit to ground as each motor phase is sequentially fired. This circuit carries the same current as the motor common. It is important to load test this circuit without back feeding the PCM or risk damaging the internals. With the key off, remove C122 and PCM connectors and conduct a voltage drop test on the Pin 4 circuit. Apply B+ (with a fused jumper) to the terminal on the servo end of the harness and with a DVOM set to DC Volts record the voltage at the PCM terminal to ground. Next re-measure voltage while a test lamp is connected from the PCM terminal to ground. The difference between the two measurements should be less than 0.3 VDC, otherwise check the wiring.
PIN 5 - Servo Clutch Control Return: The PCM will complete this circuit to ground when speed control is active. This circuit carries the same current as the deactivator switch. It is important to load test this circuit without back feeding the PCM or risk damaging the internals. With the key off, remove C122 and PCM connectors and conduct a voltage drop test on the Pin 5 circuit. Apply B+ (with a fused jumper) to the terminal on the servo end of the harness and with a DVOM set to DC Volts record the voltage at the PCM terminal to ground. Next re-measure voltage while a test lamp is connected from the PCM terminal to ground. The difference between the two measurements should be less than 0.3 VDC, otherwise check the wiring.
PIN 6 - Brake Deactivator Switch: This is a redundant shutoff switch. Without depressing the brake pedal, measure voltage on Pin 6, and re-measure with a test lamp (1156) from Pin 6 to ground, to ensure current carrying capability. The difference between the two measurements should be less than 0.3 VDC. The system requires enough current at this pin to engage properly. If voltage drop test fails, check for corroded wiring or deactivation switch. You should measure 0 volts at Pin 6 when the brake pedal is depressed firmly.
An alternate to the voltage drop test would be to disconnect the switch connector and measure the switch resistance. It should be less than 5 ohms. If the switch is suspected, a bypass test may also be done: On the harness side of the BPS connector, connect a jumper between the two deactivation switch pins and drive vehicle above 30 MPH (48 Km/h). If speed control engages then the brake deactivation switch was faulty, otherwise wiring is at fault.
Speed Control Switch Operation
NOTE
PERFORMED WITH KEY IN OFF POSITION.
Steering wheel speed control switch operation is checked at the PCM connector. Determine PCM pins which correspond to Control Switch Input and Control Switch Return. Remove PCM connector, using a DVOM set to resistance, individually press each button and measure the resistance between control switch input and return pin. See table of resistance readings below for each switch when it is depressed.