C0799

Code

Generic C — Chassis

Control Module Power Supply — Intermittent Circuit

Brand: Generic

Type: C — Chassis

Views: UK: 10 EN: 10 RU: 7

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Malfunction indicator lamp or warning lights illuminated intermittently
Modules or functions controlled by the module operate intermittently or reset
Loss of communication with the module on a scan tool during fault events
Vehicle may hard-start, stall, or show erratic behavior tied to module functions

Read and record stored freeze frame and freeze DTC occurrence conditions
Check battery state of charge and terminal condition; clean and tighten terminals
Visually inspect module connector and pins for corrosion, bent pins, or water intrusion
Perform wiggle test of harness and connector while monitoring module power/communication
Check relevant fuses and relays; inspect for loose fuse box connections
Scan for related codes (communication, voltage) and note when code sets (key on, driving)

Battery voltage at battery: 12.4–12.8 V (engine off, charged)
Key ON (engine off) supply at module pin: ~ battery voltage (minus small harness drop)
Cranking voltage: should not drop below ~9.5–10 V (dependent on vehicle)
Ground resistance from module chassis/ground pin to battery negative:
Supply ripple/noise: low — no large spikes or dropouts; use oscilloscope to identify intermittent drops

Retrieve DTC details (freeze frame, MIL count, occurrence memory) and record conditions when fault happened
Perform baseline electrical checks: battery voltage, charging system output, and main grounds
Inspect module connector: disconnect, inspect pins and terminals, then reconnect; check for corrosion, bent pins or water intrusion
Probe the module power and ground with a DVOM and wiggle the harness/connectors while observing voltage for intermittent changes
If intermittent voltage events observed, use an oscilloscope or voltage logger to capture transient drops or noise during key cycles and driving conditions
Inspect wiring route for chafing, pinched areas, or contact with moving components; repair any damaged sections and secure harness with proper routing/clips
Check associated fuses/relays and related control units; backprobing at the fuse/relay input to determine where the loss originates
If wiring and supply checks are good, consider swapping with a known-good module only if supported by manufacturer procedures; follow immobilizer or module programming rules when replacing
Clear codes and perform a test drive or recreate the conditions; monitor the module power/communications for recurrence
If intermittent problem persists after repair, escalate to manufacturer-specific technical bulletins or perform advanced power distribution diagnostics