Neon L4-2.0L SOHC (1995)
A/C Signal: Description and Operation
Related Trouble Code Message Descriptions
A/C Clutch Relay Circuit
NAME OF CODE:
A/C Clutch Relay Circuit
WHEN MONITORED:
With the ignition key ON and battery voltage greater than 10 volts.
SET CONDITION:
An open or shorted condition is detected in the A/C clutch relay control circuit.
THEORY OF OPERATION:
The A/C compressor clutch relay controls the 12-volt source for the A/C clutch. If the vehicle is equipped with a power distribution center (PDC),
the relay will be located in the PDC. One side of the relay control coil is supplied with 12 volts when the ignition switch is turned to the "RUN"
position. The circuit is completed when the other side of the relay coil is grounded by the powertrain control module (PCM). When A/C is
requested, the PCM will adjust the idle speed to accommodate the A/C compressor load on the engine. The PCM grounds the relay control circuit
after the PCM receives an A/C select signal and adjustment of the idle speed has been implemented.
POSSIBLE CAUSES:
-
Relay coil open or shorted
-
Fused ignition switch output circuit open
-
Compressor clutch relay control circuit open or shorted
-
Inoperative circuit driver in powertrain control module
No 5 Volts to A/C Pressure Sensor
NAME OF CODE:
No 5 Volts to A/C Pressure Sensor
WHEN MONITORED:
With the ignition ON.
SET CONDITION:
The A/C pressure sensor signal at PCM cavity 42 goes below 0.705 volts for more than 21.97 seconds
THEORY OF OPERATION:
The A/C pressure sensor informs the PCM if the A/C system pressure is too low or too high. This information allows the PCM to determine if it
can engage the compressor clutch.
-
If the A/C system pressure is too low, the PCM will not engage the compressor clutch.
-
If the system pressure is too high, the PCM will disengage the compressor clutch and turn ON the cooling fans to prevent the compressor head
pressure from becoming too high.
The sensor provides a signal to PCM cavity 42.
The sensor receives a 5 volt supply from PCM cavity 61.
The sensor ground is provided by PCM cavity 43.
POSSIBLE CAUSES:
-
Open 5 volt supply
-
A/C pressure sensor failure
