DTC 67

DTC 67 A/C Refrigerant Pressure Sensor Circuit:

Wiring Diagram A/C Pressure Sensor Circuit:

Circuit Description:

The ECM can determine if the A/C compressor clutch is engaged or not engaged through the A/C clutch status line. If the ECM has grounded the coil of the A/C clutch control relay, current can flow through the relay contacts to the A/C compressor clutch and the ECM on the A/C status circuit.

When voltage is present at the ECM A/C clutch status terminal, A/C status "ON" will be displayed on the scanner. As the ECM detects that the A/C compressor clutch has cycled "OFF," the ECM will record A/C system pressure from the A/C refrigerant pressure sensor. If the A/C refrigerant pressure does not increase more than 4 psi when the A/C clutch turned back "ON," a DTC 67 will set. This condition can occur if the A/C refrigerant pressure sensor is fixed at one value, or if the A/C refrigerant pressure sensor ground is open. A DTC 67 will store in the ECM memory but will not turn "ON" the MIL (Service Engine Soon) light.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1 DTC 67 will set if: the ECM does not detect an A/C refrigerant pressure change of more than 4 psi when the A/C clutch has been cycled.

2. If the relay power feed CKT 139 is intermittent, the A/C clutch status terminal may not detect voltage when A/C is commanded "ON."

3. If the A/C clutch status line becomes intermittently open or shorted while the compressor is "ON," the ECM will be wrongly detecting the A/C clutch going "ON" and "OFF" When the ECM falsely detects the clutch cycling from "ON" to ""OFF" and the clutch is remaining "ON" DTC 67 will set since no pressure change was detected.

4. If the A/C compressor clutch is disconnected or if CKT 59 or 603 or low pressure cut-off switch is open between the splice and the clutch, the A/C compressor clutch will not engage, but the ECM will detect voltage on the A/C status line which will indicate the clutch is "ON." If the A/C controls are cycled from "OFF" to "ON" at this point, a DTC 67 will set since the clutch did not engage and therefore no pressure change was detected.