Powertrain Controls - ECM/PCM

Diagnostic Trouble Code (DTC) 67:

A/C Circuit:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) can determine if the Air Conditioning (A/C) compressor clutch is engaged or not enaged through the A/C clutch status line. If the PCM has grounded the A/C relay, current can flow through the A/C relay to the A/C compressor clutch and back to the PCM on the A/C status circuit.

When voltage is present at the PCM A/C clutch status terminal, A/C status "ON" will be displayed on the Tech 1 scanner. As the PCM detects that the A/C clutch has cycled "OFF," the PCM will record A/C refrigerant pressure from the A/C refrigerant pressure sensor. If the A/C refrigerant pressure does not increase more than 27.6 kPa (4 psi) when the A/C clutch is turned back "ON," a Diagnostic Trouble Code (DTC) 67 will set. This condition can occur if the A/C refrigerant pressure sensor is fixed at one value.

DTC 67 WILL SET WHEN
The PCM does not detect an A/C refrigerant pressure change of more than 4 psi when the A/C clutch has been cycled "OFF" for 10 seconds, then "ON" for 10 seconds.

ACTION TAKEN (PCM DEFAULT)
DTC 67 will be stored in the PCM memory but will not turn "ON" the Malfunction Indicator Light (MIL), A/C operation will be disabled.

DTC CHART TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.

1. If the A/C compressor clutch is disconnected or if CKT 59 is open between the splice and the clutch, the A/C compressor clutch will not engage, but the PCM 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.

2. If the relay power feed CKT 141 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 PCM will be wrongly detecting the A/C clutch going "ON" and "OFF." When the PCM falsely detects the clutch cycling from "ON" to "OFF" and the clutch is remaining "ON," a DTC 67 will set since no refrigerant pressure change was detected.

4. Visually check A/C compressor electrical harness for problems that may prevent it from engaging.

DIAGNOSTIC AIDS
Inspect the harness and all related connectors including the PCM connections. These may cause an intermittent. Check for damaged or pushed out terminals.