P079A

What it means

Friction element A (the first clutch or band in the gear matrix) shows measurable slip while it should be fully engaged. Detected by comparing input/output speed sensors against the commanded gear ratio. Slip means the element cannot transmit full torque — risk of glazing the friction surfaces.

Is it safe to drive?

This code points to a problem that can cause damage or affect safety. Avoid driving and have the vehicle diagnosed promptly.

Most likely causes

• Worn friction discs in element A

  high

  One of the most commonly reported causes for this code — check this first.

• Low hydraulic pressure to element A

  medium

  A plausible cause — test and verify before replacing parts.

• Old ATF lacking friction modifier

  medium

  A plausible cause — test and verify before replacing parts.

Related help

• Full P079A diagnosis, causes & costs
• How to read check engine light codes
• Is it safe to drive with the light on?