Fault-code directory · Transmission electronics assessment
A pressure-switch or pressure-sensor code may accompany harsh changes or a gearbox warning. The controller is comparing pressure-related information with what it expects during operation. The first task is to establish whether the information is electrically valid.
Codes covered
P0845 · P0846 · P0847 · P0848 · P0849 · P0870 · P0871 · P0872 · P0873 · P0874
These groups concern transmission pressure sensing channels B and C. They cover circuit, range, low, high and intermittent conditions. The channel lettering must be matched to the gearbox’s own component layout. It is not a universal description of a particular clutch.
Confirm the full description, suffix and reporting module for your vehicle. These are diagnostic starting points, not a parts replacement list.
Evidence that helps narrow the fault
- Record commanded gear, temperature and the pressure-switch states when the code occurs. A fault recorded at standstill may need a different test from one recorded during a specific shift.
- Check supplies and signal paths before interpreting a permanently high or low reading as genuine hydraulic pressure.
- Where required, compare the electronic report with a correctly performed hydraulic test. Use the specified test point, equipment and operating conditions.
Choosing the next repair step
The eventual repair might involve the sensor assembly, an internal harness, the valve body or a controller input. Do not treat all four as interchangeable solutions. If bench testing is proposed, establish whether it can evaluate the reported condition or whether the complete gearbox is needed.
Will a good resistance reading prove the pressure sensor is healthy?
Not by itself. The test must suit the sensor type and the fault. A component can pass a static test but give an unreliable signal during operation.
Talk through the fault with AXION
Send the make, model, year, full scan report and a short description of when the fault happens. Include recent repairs or programming attempts. If you do not have a scan, describe the symptoms in your own words.
Workshop assessments are arranged by appointment in Didcot, Oxfordshire. UK-wide postal module testing and remote support are available for suitable work after compatibility and scope are agreed. Please contact us before removing or posting a module.
Assessment options and appointments · Garage and trade support
Related reading
- Shift solenoid D and E faults after transmission work
- Pressure-control solenoid circuit codes across channels A, B and C
Reference for generic code terminology: Snap-on diagnostic code reference. Use the manufacturer’s current service information for the actual vehicle and test procedure. This article provides general diagnostic guidance and is not a report of a particular customer repair.