dtc p0740 p0785

[yaya]

i have a 84 chevy truck with the 5.3 4l60e swap. the truck runs fine but when i put it in gear it dies. i pulled codes and got p0740 and p0785

[I-win]

Since you have both codes set I would start with checking fuse IGN 0. This is off of Alldata, but it didn't copy the diagnostic steps. Check that fuse first though. Both codes will set with that fuse blown.


DTC P0740

Circuit Description with 4L60-E / 4L65-E Automatic Transmission
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 the OFF/ON/START voltage circuit. The Powertrain Control Module (PCM) controls the solenoid by providing the ground path on the TCC solenoid valve control circuit. The PCM monitors the throttle position sensor voltage, the vehicle speed, and other inputs in order to determine when to energize the TCC solenoid valve.
When the PCM 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 B DTC.

Conditions for Running the DTC


The system voltage is 10-18 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 PCM commands the solenoid ON and the voltage feedback remains high (B+).

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

Action Taken When the DTC Sets


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


The PCM 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 PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
The PCM 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 PCM.
Diagnostic Aids
With the TCC engaged, the TCC slip speed should be -20 to +50 RPM.

Test Description
The numbers below refer to the step numbers on the diagnostic table.


This step tests for voltage to the solenoid.
This step tests the ability of the PCM and wiring to control the ground circuit.
This step tests the resistance of the TCC solenoid valve and the Automatic Transmission (AT) wiring harness assembly.

[yaya]

the engine and trans is out of a 2004 suburban i was able to get the underhood fuse block from what i read the trans was originally powered from a fuse box that was inside the truck. i dont know what wire it would be on the underhood fuse box could somebody chime in

[busta9876]

does the truck kind of jump when you put it in gear, like quickly letting out of the clutch in a manual trans vehicle? If so, might be the torque converter clutch stuck on. This could be caused by a short to ground in the TCC solenoid control circuits. You might try lifting the rear wheels off the ground, and try putting it in gear, see if it will stay running, but die when you use the brakes to bring wheels to a stop.

I have reworked harnesses before came from a truck in an accident. its not un-common for the wires going down to the trans connector to be damaged during removal. I've seen some that pinched every wire leading to trans, and exposed the copper wire. just something to check.

KEEP SAFETY IN MIND WHEN ALLOWING WHEELS TO TURN WITH VEHICLE RAISED. USE JACK STANDS, CLEAR ANYTHING IN FRONT OF TRUCK IN CASE IT WAS TO FALL OFF JACK.