Fuel Solenoid Driver Circuit Operation
The fuel solenoid driver receives an inject-command signal from the PCM on CKT 984 (figure 5-29). The driver provides current-regulated output to the fuel solenoid that controls fuel pump metering injection. The driver also returns an injection pulse-width modulated (PWM) signal back to the PCM on CKT 985. This signal tells the PCM when the fuel solenoid plunger seats. The PCM uses a calibrated injection pump-mounted resistor to determine fuel rates. The resistor value of the pump is stored in PCM memory. If PCM memory has been disturbed or the PCM has been replaced, the PCM will relearn the resistor value on the next ignition cycle and store this value.
DTC 35 — “Injection Pulse Width Error (Response Time Short)”
DTC 35 sets when battery voltage is greater than 10 volts, coolant temperature is at or above 20°C (68°F), and response time of the fuel injection solenoid is less than 1.2 milliseconds as indicated by the voltage signal on CKT 985.
DTC 36 — “Injection Pulse Width Error (Response Time Long)”
DTC 36 sets when battery voltage is greater than 10 volts, coolant temperature is at or above 20°C (68°F), and response time of the fuel injection solenoid is greater than 2.5 milliseconds as indicated by the voltage signal on CKT 985.
DTC 56 — “Injection Pump Calibration Resistor Error”
DTC 56 sets when the injection pump resistor value is not present. This could be caused by the PCM having lost its memory or the PCM being unable to read a resistor value on CKT 985 on the next ignition cycle. When DTC 56 is set, a current and history DTC will store and the “Service Engine Soon” malfunction indicator lamp will illuminate. The PCM will default to the lowest fuel table, and possible poor engine performance will be noticed.The current DTC 56 will clear on the next ignition cycle. However, the history DTC 56 will remain in the PCM.