P1640

DTC P1640 QDM #1 Diagnostic Chart (Part 1 Of 3):

DTC P1640 QDM #1 Diagnostic Chart (Part 2 Of 3):

DTC P1640 QDM #1 Diagnostic Chart (Part 3 Of 3):

QDM #1 Wiring Schematic:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) is used to control several components such as Boost Control Solenoid, the Evaporative Purge Valve and the Torque Converter Clutch Apply Solenoid. The PCM controls these devices through the use of a Quad-Driver Module (QDM). When the PCM is commanding a component "ON," the voltage potential of the output circuit will be "low" (near 0 volts). When the PCM is commanding the output circuit to a component "OFF," the voltage potential of the circuit will be "high" (near battery voltage). The primary function of the QDM is to supply the ground for the component being controlled.

Each QDM has a fault line which is monitored by the PCM. The fault line signal is available on the data stream for scan tool test equipment display on Tech 1 scan tool. The PCM will compare the voltage at the QDM based on accepted values of the fault line. If the QDM #1 fault detection circuit senses a voltage other than the accepted value, the fault line will go from a "low" signal on the data stream to a "high" signal and Diagnostic Trouble Code (DTC) P1640 will set.

DTC P164O WILL SET WHEN
^ The engine is running.
^ The PCM detects an improper voltage level on a circuit connected to QDM #1.
^ The above conditions met for 5 seconds.

ACTION TAKEN (PCM WILL DEFAULT TO)
The PCM will illuminate the Malfunction Indicator Lamp (MIL) with a current DTC P1640 set.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. If a QDM related DTC is stored, diagnose that problem first. The repair made to the related DTC will most likely repair DTC P1640 also.
2. If QDM #1 symptoms are present, the checks on Part 3 of 3 of this chart should isolate the cause of the fault.
3. This test will determine which circuit is out of specifications.
4. This test will determine if the problem is the circuit or the component.
5. As the factory installed PCM is protected with an internal circuit breaker, it is highly unlikely that the PCM needs to be replaced.

DIAGNOSTIC AIDS
Monitor the voltage at each terminal shown above while moving related harness connectors, including PCM harness. If the failure is induced, the voltage will change. This may help locate an intermittent condition. Check for bent pins at PCM and PCM connector terminals. If DTC reoccurs with no apparent connector problem, replace PCM.