P0846 moderate

Transmission Fluid Pressure Sensor/Switch B Circuit Range/Performance

The P0846 code means the vehicle's onboard diagnostic system has detected: Transmission Fluid Pressure Sensor/Switch B Circuit Range/Performance. This is a moderate severity code.

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Keep driving?: Short distances only
DIY difficulty: hard
Estimated cost: $150 - $800 (parts and labor)

Check Your Fluid First

ANCEL AD310 OBD-II Scanner

Read and clear transmission codes. Many trans codes are caused by low or burnt fluid -- check level and color before assuming the worst.

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Read Transmission Codes

LAUNCH CRP123X (Reads All Systems)

Basic scanners only read engine codes. This reads transmission, ABS, and airbag too.

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Common Symptoms

Check Engine Light illuminated
Shift quality degradation
Slipping during gear changes
Inconsistent transmission behavior

Probable Causes (Ranked by Likelihood)

Pressure sensor B reading outside expected range Very High
Degraded or contaminated transmission fluid High
Partially blocked hydraulic passage Moderate
Internal valve body wear Low

Step-by-Step Diagnostic Procedure

Compare sensor B reading to actual pressure using a mechanical gauge
Perform a transmission fluid and filter service
Monitor sensor B data at various operating conditions
Check for manufacturer TSBs for pressure sensor recalibration

Frequently Asked Questions

What causes range/performance issues on sensor B?

The sensor may be providing a voltage within the valid range but the pressure reading does not match what the TCM expects. Dirty fluid, a worn pump, or internal wear can all cause this.

Is a fluid change worth trying before replacing the sensor?

Yes, degraded fluid can cause abnormal pressure readings. A fluid and filter change is a good first step and is less expensive than sensor replacement.

Can P0846 and P0841 appear together?

Yes, if both sensors A and B show range/performance issues, the root cause may be a systemic problem like low fluid, a worn pump, or contaminated fluid rather than individual sensor failures.