DTC 126

A/C Compressor Control Circuit:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) has the ability to monitor A/C refrigerant pressure. This is achieved through the use of high side and low side pressure switches. The high side pressure switch is a normally closed switch that is grounded through CKT 251 and monitored by the PCM on CKT 604. When the A/C high pressure line exceeds 430 psi, the switch opens signaling excessive high side refrigerant pressure and the PCM disables the A/C compressor clutch.
If the A/C high side pressure switch disables the A/C compressor clutch 10 times with the A/C high side temperature below 87°C (189°F) the PCM detects an over pressure condition. This system is designed to detect blockages in the A/C system.

DTC 126 WILL SET WHEN
A/C compressor clutch disabled 10 times by the A/C high pressure switch with A/C high side temperature less than 87°C (189°F).

ACTION TAKEN (PCM WILL DEFAULT TO)
- Disable A/C compressor clutch.
- DTC 126 does not illuminate the Malfunction Indicator Lamp (MIL) (Service Engine Soon).

DTC 126 WILL CLEAR WHEN
The fault no longer exists.


DIAGNOSTIC AIDS
DTC 126 is designed to disengage the A/C Compressor Clutch in the event that high side refrigerant temperature exceeds 86°C (187°F). The A/C Compressor will re-engage and the DTC will be stored as a history DTC when the high side temperature falls below 78°C (172°F) and the ignition switch is cycled "OFF" then "ON." If DTC 126 has set, possible causes for excessive high NC Head Pressure must be checked.
Possible causes for a DTC 126:
- Short to ground on CKT 732.
- Faulty High Side Temperature Sensor.