Is transmission fluid viscosity a possible cause?
Check for fault codes to see if the transmission has been operating in the “limp” mode, which is designed to protect the transmission from slipping. This could be caused by low hydraulic pressure, internal fluid leaks in the valve body, shift solenoids or accumulators, or even an engine problem such as low vacuum or a faulty throttle position sensor. Before spending big bucks on this issue, try adding half a can of Trans-Tune to the transmission fluid. Q: I’ve got this vexing problem with a check-engine light on my 2001 4Runner. The code shows oxygen sensor issues, but my local repair guys have been unable to find out why. If I turn off the check light, the car usually runs fine for weeks, even months, and then the light comes on, usually when the air is on and the engine lugs a bit if I’m accelerating. This is the third time I’ve left the car for the day with these guys, whom I’ve known and trusted for decades. They haven’t been able to locate the issue. A: If they’ve checked for DTC
