GM transmission MIL

Some owners of 2009-2010 Hummer H3 or H3T, 2009 Chevy Tahoe equipped with Police package, 2009-2010 Chevy Colorado, Express, Silverado and Trailblazer, 2009-2010 GMC Canyon, Envoy, Savanna and Sierra, and 2009 Saab 9-7X (all equipped with the 4L60E or 4L70E automatic transmission)  vehicles may comment that the MIL is illuminated and the vehicle has a harsh 1-2 shift (DTC P0741 is set in the transmission control module (TCM).

For the 2009-2010 Chevy Express and GMC Savana built prior to Sept. 14, 2009, the transmission wiring harness connector may not be properly seated. In this case, DTC P0741 is often accompanied by DTC P2764. Disconnect and reconnect the harness to assure that it is properly seated and re-test the vehicle to confirm that the code does not return.

DTC P0741 may also be caused by debris in the transmission pump blocking the TCC apply valve or the TCC apply valve orifice cup plug.

Check for foreign debris causing the TCC apply valve to stick and not move fully. If found, clear the debris and verify that the valve moves freely. If foreign material is not present in the valve, verify that the valve moves freely and is not sticking. If the valve is sticking and appears to be clean, replace the pump cover.

Inspect for foreign material blocking the orifice to the TCC apply valve. If material is found in the cup plug, clear the material and reinstall the pump cover.

If the TCC apply valve has no issue, then look for other issues per diagnostic procedures for DTC P0741 or P0742. This could include a damaged TCC PWM solenoid valve or TCC S solenoid valve or a stuck TCC regulator apply valve. If other codes are found in addition to the P0741, inspect for further damage, such as burnt clutches.

Replace the torque converter if any of the following conditions exist:

-          The vehicle has TCC shudder, replace only after all hydraulic and electrical diagnosis. The converter clutch material may be glazed.

-          You discover steel particles after flushing the cooler and cooler lines.

-          The transmission pump is damaged and you discover steel particles in the converter.

-          You discover steel particles or clutch lining material in the pan and filter.

Check for a proper transmission harness connection.
<p>Check for a proper transmission harness connection.</p>
Look for foreign material casing the TCC apply valve (1) to stick and check the orifice to the TCC valve.
<p>Look for foreign material casing the TCC apply valve (1) to stick and check the orifice to the TCC valve.</p>



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