DTC 70

Trouble Code Chart 70:

Air Conditioning Control Wiring:

CIRCUIT DESCRIPTION
The A/C pressure sensor responds to changes in A/C refrigerant system high side pressure. This input indicates how much load the A/C compressor is putting on the engine and is one of the factors used by the ECM to determine IAC A/C valve position of idle speed control. The circuit consists of a 5 volts reference and a ground, both provided by the ECM, and a signal line to the ECM. The signal is a voltage which is proportional to the pressure. The sensor's range of operation is 0 to 450 psi. At 0 psi, the signal will be about .1 volt, varying up to about 4.9 volts at 450 psi or above. DTC 70 sets if the voltage is above 4.9 volts for 5 seconds or more. The A/C compressor is disabled by the ECM if DTC 70 is present or if pressure is above calibrated values described in "ECM Controlled Air Conditioning,".

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. This step checks the voltage signal being received by the ECM from the A/C pressure sensor.

2. Checks to see of the high voltage signal is from a shorted sensor or a short to voltage in the circuit. Normally, disconnecting the sensor would make a normal circuit go to near zero volt.

DIAGNOSTIC AIDS:
DTC 70 sets when signal voltage falls outside the normal possible range of the sensor and is not due to a refrigerant system problem. If problem is intermittent, check for opens or shorts in harness or poor connections.