A012

Diagnostic Chart:

CIRCUIT DESCRIPTION
The Lo Side Temperature sensor is a thermistor that controls a signal voltage to the ACP The ACP applies a voltage on CKT 731 to the sensor. When the sensor is cold its resistance is high, therefore the ACP will see a high signal voltage at pin "D15." As the sensor warms, its resistance becomes less and the signal voltage is pulled low through the sensor ground, CKT 407. This signal voltage will vary between 5V (open circuit) and 0V (short circuit).

TEST CONDITION(S)
1. Ignition "ON."

FAILURE CONDITION(S)
The signal voltages indicates less than -38°C (open circuit) or greater than 93°C (short circuit).

ACTION TAKEN
1. A/C compressor not allowed to engage. IPC will display "SERVICE A/C SYSTEM - A/C COMPRESSOR OFF."
2. A substitute temperature reading (filtered outside temperature) will be implemented. (AD28 will display the actual sensor reading.)

NOTES ON FAULT TREE
1. ACP data value AD28 displays Lo Side temperature. The valid operating range is from -38°C to 93°C.
2. A reading too low indicates an open circuit. Jumpering the harness connector will determine whether the wiring or sensor is the cause of the open.
3. A reading too HI indicates a short circuit. Removing the sensor will determine whether the wiring or sensor is the cause of the short.
4. The open has been determined to be in the wiring. Providing a ground at the jumper will determine if the open is in the ground wiring or the sensing wire.
5. Grounding the connector at the ACP will determine if the open is in the sense circuit or at the ACP connection/ACP internal.
6. Note values of AD25, AD26, AD27, and AD28. If all read near 40 repair open CKT 407 between ACP and C201 "D." If AD27 and AD28 read near -40 repair open CKT 407 between C20t "D" and S218. If only AD28 reads near -40 repair open CKT 407 between S218 and Lo-Side sensor.

NOTES ON INTERMITTENTS
If an intermittent code A012 is being set, Select ACP Snapshot Data for Code A012 and note value of AD28. A reading of approx -40°C indicates an intermittent open, a reading above 93°C indicates an intermittent short.

Manipulate the related wiring while observing ACP data AD28. If the failure is induced, the reading will jump outside its normal range.

If the value of the sensor, displayed by AD28, is not reasonably close to the corresponding gage pressure reading, check for poor terminal contact or replace sensor.