P2A68

Code

Generic P — Powertrain

Alternative Fuel Tank C Level Sensor Circuit Intermittent/Erratic

Brand: Generic

Type: P — Powertrain

Views: UK: 16 EN: 36 RU: 22

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Causes

Loose, corroded or disconnected connector at the tank C fuel level sensor
Damaged, chafed or shorted wiring harness between sensor and control module (intermittent contact)
Failing fuel level sender (worn float, internal corrosion, intermittent element)
Faulty ground or reference voltage to the sensor
Intermittent fault in the body/computer module or fuel gauge module
Corrosion or contamination inside the tank causing intermittent contact

Symptoms

Fuel level gauge fluctuates, jumps, or reads erratically for tank C
Malfunction Indicator Lamp (MIL) may be illuminated or a pending code stored
Incorrect range-to-empty or fuel warnings for tank C
Possible no-change or stuck reading for tank C under normal refueling/use
Intermittent communication of fuel level data to other vehicle systems

What to check

Read and record freeze frame and live data for tank C fuel level with a scan tool
Visually inspect connectors at the tank C sender and any intermediate junctions for corrosion or looseness
Wiggle harness while watching live data to reproduce the intermittent
Check reference voltage and ground at the sensor connector with ignition on
Compare tank C readings to other tanks (if multi-tank system) to isolate sensor-specific problem

Signal parameters

Sensor type: variable resistor (analog) or PWM output depending on vehicle; behavior should be smooth with float movement
Reference voltage typically 5 V (verify on vehicle wiring diagram); signal should be stable without noise
Analog resistance/signal should change progressively as float moves — no abrupt jumps or open circuit
PWM sensors: expect stable frequency and a duty cycle that varies with level; excessive noise or missing pulses indicates a fault
Open-circuit or short-to-ground/short-to-VB will be flagged by module as abnormal

Diagnostic algorithm

Obtain the vehicle-specific wiring diagram and sensor specification (type, reference voltage, expected resistance or PWM parameters).
Retrieve stored data: read freeze frame, pending/confirmed status and live fuel level data for Tank C with a scan tool. Note when the erratic behavior occurs (key-on, driving, refueling).
Perform a visual inspection: remove trim/panels as required to access the Tank C sender connector. Look for corrosion, bent pins, water intrusion, loose clip or damaged seals.
With ignition ON (engine off), back-probe the sender connector. Verify reference voltage, signal voltage and ground integrity. Compare to specification. Do not short pins together.
Wiggle-test the harness and connector while monitoring live data and signals. If the signal fluctuates with movement, suspect wiring or connector mechanical issue.
Measure sender resistance while moving the float (if accessible). Resistance should change smoothly with float travel. Sudden jumps or open/short indicate a bad sender.
If the sensor is PWM type, use a lab scope (or scan tool that can display waveform) to confirm frequency and duty-cycle behavior while moving the float. Look for noise, missing pulses or intermittent loss.
Inspect and repair any damaged wiring, pins or corroded connectors. Replace or re-pin connector terminals if corrosion or poor contact is found. Protect repairs from fuel and moisture.
If wiring and connectors check out, temporarily substitute a known-good sensor (if available) or carefully bench-test the sender. Replace the sender assembly if it shows intermittent internal behavior.
After repairs, clear codes and perform a drive/operational cycle while monitoring Tank C data to confirm the fault does not return. If intermittent returns, consider module-level diagnostics (BCM/gauge cluster) and check for software updates or technical service bulletins.
If module replacement is considered, confirm all wiring and sensors are good first. Reprogram/configure replacement modules per manufacturer procedure.

Likely causes

Wiring harness damage or loose connector at tank C (most common for intermittent/erratic codes)
Corroded/contaminated sensor or float assembly causing intermittent resistance changes
Faulty ground or reference circuit to the sensor
Intermittent failure of the instrument cluster or BCM input circuit (less common)