P0740 Explained

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P0740 Explained

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Blazer >> Mechanical & Maintenance >> Do-It-Yourself >> P0740 Explained

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P0740 Explained - 4/17/2008 8:11:24 PM

swartlkk

Posts: 13682
Joined: 5/1/2005
From: Waterloo, NY
Status: online

P0740 - Torque Converter Clutch Circuit

Schematic

CIRCUIT DESCRIPTION
The Torque Converter Clutch (TCC) solenoid valve is an electrical device that is used with the Torque Converter Clutch Pulse Width Modulation (TCC PWM) solenoid valve in order to control TCC apply and release. The TCC solenoid valve attaches to the transmission case assembly extending into the pump cover. The TCC solenoid valve receives ignition voltage through circuit 1020. The Vehicle Control Module (VCM) controls the solenoid by providing the ground path on circuit 422. The VCM monitors the Throttle Position (TP) voltage, the vehicle speed, and other inputs in order to determine when to energize the TCC solenoid valve.

When the VCM detects a continuous open, short to ground, or short to power in the TCC solenoid valve circuit, then DTC P0740 sets. DTC P0740 is a type A DTC.

CONDITIONS FOR RUNNING THE DTC

* The system voltage is 10-19 volts .
* The engine speed is greater than 450 RPM for 5 seconds .
* The engine is not in fuel cutoff.

CONDITIONS FOR SETTING THE DTC
DTC P0740 sets if one of the following conditions occurs for 5 seconds :

Condition 1
The VCM commands the solenoid ON and the voltage feedback remains high (B+).

Condition 2
The VCM commands the solenoid OFF and the voltage feedback remains low (0 volt ).

ACTION TAKEN WHEN THE DTC SETS

* The VCM illuminates the Malfunction Indicator Lamp (MIL) .
* The VCM inhibits TCC engagement.
* The VCM inhibits 4th gear if the transmission is in hot mode.
* The VCM freezes shift adapts from being updated.
* The VCM records the operating conditions when the Conditions for Setting the DTC are met. The VCM stores this information as Freeze Frame and Failure Records.
* The VCM stores DTC P0740 in VCM history.

CONDITIONS FOR CLEARING THE MIL/DTC

* The VCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
* A scan tool can clear the MIL/DTC.
* The VCM clears the DTC from VCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
* The VCM cancels the DTC default actions when the fault no longer exists and/or the ignition switch is OFF long enough in order to power down the VCM.

DIAGNOSTIC AIDS

* Inspect the connector at the VCM and all other circuit connecting points for an intermittent condition. Refer to Testing for Intermittent and Poor Connections in Diagrams.
* Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical Intermittents in Diagrams.
* With the TCC engaged, the TCC slip speed should be -20 to +50 RPM .
* A faulty ignition switch may set this code.

Diagnostic Chart (Part 1 Of 3)

Diagnostic Chart (Part 2 Of 3)

Diagnostic Chart (Part 3 Of 3)

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.

< Message edited by swartlkk -- 4/17/2008 8:19:32 PM >

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