I have a P1640 code will not stay out changed.

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1995 BUICK RIVIERA
145,000 MILES

I have a p1640 code will not stay out changed relays for fans, changed vent solinoid for evap purg, all that is left is booster solinoid or trans, over drive. Car has new trans jasper I checked computer looks good. What should the boost be at idel

Friday, March 29th, 2013 AT 4:22 PM

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ASEMASTER6371

MECHANIC
52,797 POSTS

Who told you to replace these items?

Here is the description

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) is used to control several components such as those in the image. 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 #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 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 (Service Engine Soon) 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 in "Chart 3 of 3" of should isolate the cause of the fault.
DTC P1640 Chart (2 of 3)

3. This test will determine which circuit it out of specifications
DTC P1640 Chart (3 of 3)

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.