Both codes (obviously) point to transmission
related problems. The DTC P0700 means Transaxle Control System Fault
Conditions and the DTC P0742 code means Torque Converter Clutch (TCC) - Stuck On.
The DTC P0700 code is for information only and the next step is
to check for transaxle codes in the Transaxle Control Module (TCM). So you'll
have to have the dealer or another qualified shop/technician pull the transaxle
codes from the TCM and go from there.
On DTC P0742, Torque Converter Clutch Solenoid Valve (TCC Sol. Valve) is a normally-open exhaust valve that is used with the Torque Converter Clutch Pulse Width Modulation Solenoid Valve (TCC PWM Sol. Valve) in order to control fluid acting on the converter clutch apply valve. The TCC Sol. Valve attaches to the transmission case assembly extending into the pump cover. When grounded (energized) by the Vehicle Control Module (VCM), the TCC Sol. Valve stops converter signal oil from exhausting. This causes converter signal oil pressure to increase and move the converter clutch apply valve against spring force and into the apply position. In this position, release fluid is open to an exhaust port and converter feed fluid fills the apply fluid circuit. The converter feed fluid applies the TCC. When the VCM no longer provides a ground path, the TCC Sol. Valve de-energizes and apply fluid exhausts, releasing the TCC.
Condition: Some customers may comment that the transmission shifts hard, a shudder/chuggle is felt on deceleration or the Service Engine Soon (SES) light is illuminated.
A technician may find DTC P0742 set. Customers with 4T80E transaxles may also comment on a "bump" feeling at approximately 61-68 km/h (38-42 mph) when they lift and then tip into the throttle. There may also be a concern of whine noise in 3rd or 4th gear with or without the Service Engine Soon light/message displayed and with DTC P0742 set.
Correction:
Note: DO NOT REPLACE THE VALVE BODY AND PUMP ASSEMBLY.
Important: This test is not applicable to the 4T80E transmission. Instead, replace the TCC PWM solenoid on vehicles with a 4T80E transmission using published procedures for the vehicle being serviced.
Perform one of the following diagnostics:
• Test drive the vehicle with the Tech 2® installed, Monitor TCC Release Pressure. The Status will be YES until TCC applies and then the display will read NO. If during acceleration the status remains NO and the upshifts are harsh and during deceleration the vehicle shudders during downshifts, suspect the TCC PWM solenoid.
• With the Tech 2 installed in the vehicle, start the engine. Build the vehicle on the Tech 2®. Apply and firmly hold the service brake. Place the transaxle in D4 and command Drive 3 with the Tech 2®. If the engine stumbles and/or stalls, suspect the TCC PWM solenoid.
Replace the TCC PWM solenoid using published procedures for the vehicle being serviced.
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Jose.
2005 Equinox's are known for water leakage problems around the cowl and windshield areas. Water leaks in and causes shorts in the main wiring harness and eventual corrosion between the fuse panel's grounding to the floor under the shifter console. Reroute a new ground wire to the body from the fuse panel in the shift console. Find the source of water leak. GM paid to have mine fixed.
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