P079E: Clutch 5 slips despite a locked-state command

P079E generically identifies transmission friction element E slip. The 2018 GM HPC1 section labeled “CT6 Unique” describes this code as clutch 5 slip. That source-specific mapping should be confirmed for the actual transmission before using its criteria.

A locked clutch should meet the slip expectation

The documented speed branch fails at clutch slip of at least 50 rpm. Its enable conditions include clutch status locked, estimated line pressure at least 350 kPa, estimated clutch torque above 50 Nm, unfaulted motor speeds, no wheel slip and no shutdown command.

The steady branch requires 0.80 seconds of failure in a 0.80-second window; a transient branch uses 0.80 seconds in one second. GM lists Type A, one-trip reporting. These are monitored estimates and states, not instructions to reproduce a high-load test on public roads.

Why context prevents a wrong conclusion

Slip during an intentional transition is different from slip while the controller considers the clutch locked. Invalid motor-speed information can also undermine a calculated slip result, which explains the source's validity condition. Preserve command state, slip, pressure/torque estimates and companion faults.

The table also includes an energy branch with an inconsistent clutch reference; no energy-based repair conclusion is made here. Use the vehicle-specific transmission procedure to identify the cause and verify repair. P079E does not itself prove a worn friction pack or select a replacement component.

Source and applicability

This explanation follows the documented GM monitor, not a verified application to every vehicle with this code. Confirm the vehicle, reporting module and calibration in current service information. GM diagnostic table, physical page 1818.