P1670

Code P1670, Quad Driver Module (QDM) #4 Circuit (Part 1 Of 3):

Code P1670, Quad Driver (QDM) #4 Circuit (Part 2 Of 3):

Code P1670, Quad Driver (QDM) #4 Circuit (Part 3 Of 3):

Quad Driver Circuit #4:

*** This information has been updated according to Technical Service Bulletin #416507, dated April 1994.

CIRCUIT DESCRIPTION
The PCM is used to control several components such as those illustrated above. 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. The PCM will compare the voltage at the QDM based on accepted values of the fault line. If the QDM #4 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 DTC P1670 will set.

DTC 1670 WILL SET WHEN:
^ The engine is running.
^ The PCM detects an improper voltage level on a circuit connected to QDM #4.
^ The above conditions met for 5 seconds.

ACTION TAKEN (PCM will default to):
DTC P1670 does not illuminate the MIL (Service Engine Soon).

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. If QDM #4 related symptoms are present the checks on Part 3 of 3 of this DTC chart should isolate the causes of the malfunction.
2. This test will determine which circuit is out of specification.
3. This test will determine if the problem is the circuit or the component.
4. 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.