P0792

What it means

P0792 is the generic SAE J2012 code for an Intermediate Shaft Speed Sensor 'A' circuit range or performance fault. The transmission control unit compared the signal from the intermediate shaft speed sensor with other inputs, such as input shaft speed, output shaft speed, engine speed and the selected gear, and found it implausible. The signal is present but does not match what the control unit expects. Where the sensor sits and what it measures depends on the transmission design, so this code is only found on certain automatic, dual-clutch and automated manual gearboxes.

Symptoms

• Gearbox warning light or malfunction indicator lamp on
• Harsh, delayed or flared gear changes
• Gearbox stuck in one gear or in limp-home mode
• Erratic or non-working speedometer or rev-related gearbox behaviour
• Torque converter lock-up not engaging, with poorer economy
• Transmission slipping or shifting at the wrong times

Possible causes

• Damaged, contaminated or failing intermediate shaft speed sensor, including metal debris on a magnetic tiplikely
• Wiring or connector fault in the sensor circuit, such as chafing, corrosion, a poor pin fit or oil ingresslikely
• Incorrect sensor air gap or a loose or badly seated sensorpossible
• Low, degraded or contaminated transmission fluid causing slip, so shaft speeds do not matchpossible
• Internal transmission wear or clutch slip, or a damaged tone ring or reluctor wheelpossible
• Faulty transmission control unit or a software issue (check for a known calibration update for the model)rare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting gear, speed and fluid temperature when the fault set.
2. Look for other speed sensor or gear ratio codes, which point towards slip or a shared circuit fault.
3. Check the transmission fluid level and condition as the manufacturer specifies, since procedures vary by model.
4. Inspect the sensor, wiring and connector for damage, oil contamination, corrosion, chafing and a secure fit.
5. Check the sensor tip for metallic debris and the sensor and mounting for damage or the correct air gap.
6. Using live data on a road test, compare intermediate shaft speed with input shaft, output shaft and engine speed in each gear.
7. Test the sensor circuit for resistance, supply, ground and signal against the manufacturer's specification for that model.
8. If the sensor and wiring are good, check for gearbox slip, damaged tone rings and any applicable software updates.

How to fix

• Repair or replace damaged wiring, terminals or the connector, and seal out any oil or moisture.
• Replace the intermediate shaft speed sensor and refit it correctly, with a new seal where needed.
• Correct the transmission fluid level, or change the fluid and filter if it is degraded, following the manufacturer's procedure.
• Clean any debris from the sensor area and investigate the source of the contamination.
• Repair or overhaul the transmission if there is internal wear or a damaged tone ring.
• Update the control unit software if a known calibration issue applies to the vehicle.

Can I keep driving?

Nearby codes

• P0791GenericIntermediate Shaft Speed Sensor A Circuit
• P0793GenericIntermediate Shaft Speed Sensor A Circuit No Signal