P079D: Clutch four is judged over a short slip interval

The C4 slip monitor assigns P079D when clutch four continues slipping under its documented commanded-on conditions. Its timing is shorter than the neighboring clutch-slip entries, so a slowly updated scan display may not preserve the event's detail.

A specific command-response relationship

The table requires C4 slip above 100rpm for 0.3125 seconds. It also requires pressure command of at least 1800kPa, torque estimate of at least 20Nm and a detected fill state. These conditions identify the situation in which the controller expects the clutch to transfer torque with much less slip.

The pass criterion is stricter than merely falling below 100rpm: C4 slip must be below 10rpm for 0.125 seconds, with the stated supporting conditions. Keep that distinction when interpreting an event that improves without fully meeting the monitor's pass definition.

Preserve timing rather than only the peak

Record C4 command and slip data with the highest practical diagnostic sampling quality supported by the correct tool. An isolated peak cannot establish how long the qualifying relationship lasted. Likewise, commanded pressure is not evidence that the hydraulic circuit achieved that pressure.

The source does not select a failed clutch, valve or controller. Those alternatives require the matching diagnostic procedure and physical evidence. Testing must account for propulsion torque and hybrid electrical hazards; this monitor description does not authorize an improvised stall or forced-engagement test.

Source and applicability

GM 2010 10OBDG10 Hybrid Diagnostics, only the cited controller and monitor. These are historical calibration examples; individual vehicle, engine and hardware applicability is not established. GM PDF, page 197.