Functional Operation

When the PCM detects the the malfunction(s) listed, the PCM carries out fail safe/back-up control. In addition, the corresponding DTC number(s) can be identified by using the scan tool.

DIAGNOSTIC ITEMS FOLLOWED BY CONTROL DURING MALFUNCTION:
No cam signal at PCM
The PCM uses the crankshaft position sensor signal only to control fuel injection timing, etc. (Accordingly, normal sequential multiport fuel injection may not be carried out.)

Throttle position sensor voltage low
The PCM uses the value calculated from the MAP sensor signal instead of the throttle valve opening angle (voltage).

Throttle position sensor voltage high
The PCM uses the value calculated from the MAP sensor signal instead of the throttle valve opening angle (voltage).

Engine coolant temperature (ECT) sensor voltage too low
- The PCM uses the default value [46° C (114°F)] as the engine coolant temperature.
- The PCM operates the radiator fan.
- The PCM carries out open loop control.

Engine coolant temperature (ECT) sensor voltage too high
- The PCM uses the default value [46° C (114° F)] as the engine coolant temperature.
- The PCM operates the radiator fan.
- The PCM carries out open loop control.

Front bank upstream HO2S stays at center
The PCM carries out open loop control.

No vehicle speed sensor signal
The PCM controls the engine as if the vehicle speed were 0 mph.

MAP sensor voltage too low
The PCM uses the value calculated from the throttle position sensor and the engine speed signals instead of the MAP value (mV).

MAP sensor voltage too high
The PCM uses the value calculated from the throttle position sensor and the engine speed signals instead of the MAP value (mV).

No change in MAP from start to run
The PCM uses the value calculated from the throttle position sensor and the engine speed signals instead of the MAP value (mV.)

Intake air temperature sensor voltage low
The PCM uses the engine coolant temperature instead of the intake air temperature.

Intake air temperature sensor voltage high
The PCM uses the engine coolant temperature instead of the intake air temperature.

Front bank upstream HO2S shorted to voltage
The PCM carries out open loop control.

Rear bank upstream HO2S stays at center
The PCM carries out open loop control.

Rear bank upstream HO2S shorted to voltage
The PCM carries out open loop control.

Battery temperature sensor volts out of limit
The PCM uses the default value [62°C (144°F)] as the battery temperature.

Low speed fan control relay circuit
The PCM turns on the high speed fan control relay instead of the low speed fan control relay

Front bank upstream HO2S slow response
The PCM carries out open loop control.

Rear bank upstream HO2S slow response
The PCM carries out open loop control.

High speed radiator fan control relay circuit
The PCM turns on the low speed fan control relay instead of the high speed fan control relay

Front bank downstream HO2S shorted to voltage
The PCM carries out open loop control.

Rear bank downstream HO2S shorted to voltage
The PCM carries out open loop control.

Front bank downstream HO2S stays at center
The PCM carries out open loop control.

Rear bank downstream HO2S stays at center
The PCM carries out open loop control.

Throttle position sensor volt age does not agree with MAP
The PCM uses the value calculated from the MAP sensor signal instead of the throttle valve opening angle (voltage).

No 5 volts to MAP sensor
The PCM uses the value calculated from the throttle position sensor and the engine speed signals instead of the MAP value (mV).

No 5 volts to throttle position sensor
The PCM uses the value calculated from the MAP sensor signal instead of the throttle valve opening angle (voltage).

Front bank upstream HO2S shorted to ground
The PCM carries out open loop control.

Front bank downstream HO2S shorted to ground
The PCM carries out open loop control.

Intermittent loss of CMP or CKP
The PCM uses the crankshaft position sensor signal only to control fuel injection timing, etc. (Accordingly, normal, sequential, multiport fuel injection may not be carried out.)

Rear bank upstream HO2S shorted to ground
The PCM carries out open loop control.

Rear bank downstream HO2S shorted to ground
The PCM carries out open loop control.