P0392 - Camshaft Position Sensor (CMP) 'B' Circuit Low (Bank 2)
System
Powertrain (Engine & Gearbox)
Technical Description
The control module has detected a fault in the Camshaft Position Sensor (CMP) 'B' Circuit Low (Bank 2) (P0392). The signal is below the lower threshold, typically from a short to ground or an internally shorted sensor. Affects cylinder bank 2 (bank 2, radiator/left side).
Multimeter Test Points & Nominal Values
| Test Point / Component | Measurement | Nominal Target Range | Test Condition |
|---|---|---|---|
| Camshaft Position Sensor (CMP) 'B' Circuit Low (Bank 2) – Coil Resistance | Resistance (Ω) | 200 - 1800 Ω (typically 500 - 1200 Ω) | Sensor disconnected at 20°C |
| Camshaft Position Sensor (CMP) 'B' Circuit Low (Bank 2) – Output (AC Voltage) | Voltage (V) | 0.5 - 2.0 V AC at cranking, rising with RPM | During cranking / engine running |
| Insulation Resistance to Ground | Resistance (MΩ) | > 20 MΩ | Sensor pin to chassis ground |
Sensor disconnected at 20°C
During cranking / engine running
Sensor pin to chassis ground
Oscilloscope Waveform Analysis
2 ms/div, 2 V/divPossible Causes
Short to ground on the signal wire or an internal short circuit within Camshaft Position Sensor (CMP) 'B' Circuit Low (Bank 2)
Bank 2 specific:Inspect wiring harness to cylinder bank 2 (radiator/left bank, exposed to vibration and moisture).
Channel B:Verify dedicated wiring pins and signal pair for circuit B against the schematic.
Chafed or pinched wiring harness along the signal path to Camshaft Position Sensor (CMP) 'B' Circuit Low (Bank 2)
Poor ground connection or excessive voltage drop (> 0.1 V) at the ground point for Camshaft Position Sensor (CMP) 'B' Circuit Low (Bank 2)
Defective internal output driver or reference circuit in the control module for Camshaft Position Sensor (CMP) 'B' Circuit Low (Bank 2)
Symptoms
4
Recommended Solution
Compare signal voltage and resistance between circuit B and companion circuit A at module connector.
Cross-swap the component on Bank 2 with Bank 1 to rule out mechanical oil passages and internal timing wear.
Measure signal wire resistance to chassis ground with connector unplugged (must exceed 10 kΩ; low reading confirms short to ground).
Verify loaded supply voltage and harness terminal pins at Camshaft Position Sensor (CMP) 'B' Circuit Low (Bank 2).
Check circuit continuity and ground-side voltage drop (< 0.05 V) for Camshaft Position Sensor (CMP) 'B' Circuit Low (Bank 2).
Scope the signal trace during cranking to verify symmetric sine peaks without missing or deformed teeth.
Mechanic's Tip
Inductive VR sensors often test fine cold but develop an open circuit when engine heat expands the internal fine windings. Gently warm the sensor with a heat gun while monitoring resistance to expose thermal open circuits.