P0845
Transmission Fluid Pressure Sensor/Switch B Circuit
If your code reader dashboard displays the generic DTC error code P0845, your vehicle is currently experiencing an active failure related to "Transmission Fluid Pressure Sensor/Switch B Circuit". Proper system troubleshooting is required to safely clear this warning.
Driver's Summary
Code P0845 means your vehicle detected a problem with the transmission fluid pressure sensor/switch b circuit system. You may notice check engine light, harsh downshifts, transmission shudder, all of which are direct consequences of this malfunction. Given the high severity of this code, continuing to drive risks significant mechanical damage. Have it diagnosed immediately.
Symptoms
Check engine light, harsh downshifts, transmission shudder
Common Causes
- Failed TFP Sensor B
- Short or open in sensor B circuit
- Dirty fluid blocking sensor port
- Valve body failure
How to Fix
- 1 Replace TFP Sensor B
- 2 Repair wiring harness
- 3 Clean valve body and change fluid
- 4 Replace valve body
Technical Explanation
To set P0845, the PCM samples the affected circuit multiple times per second, comparing live readings against manufacturer-programmed operating windows. Shift solenoid circuits are monitored for both functional performance (does the transmission achieve the commanded gear ratio?) and electrical integrity (is the solenoid's resistance within the normal range of 10–40 ohms?). Once confirmed, the code is stored as a permanent DTC and the MIL is activated. The freeze frame snapshot — recording RPM, load, coolant temperature, and fuel trim at fault detection — is also saved and is critical for accurate diagnosis.
Is It Safe to Drive?
Driving with an active P0845 fault risks accelerating damage to failed tfp sensor b and related components. The longer the fault persists, the more expensive the eventual repair becomes — what starts as a sensor or solenoid issue can escalate to major mechanical failure.
Mechanic's Pro Tip
For P0845, test the solenoid's coil resistance with a multimeter before ordering parts — most solenoids should read between 14 and 40 ohms; an open (infinite resistance) or short (near zero) confirms it's failed electrically. Also verify the PCM is commanding the solenoid by backprobing the connector with a test light during the relevant operating condition — if there's no command signal, the fault is in the PCM or wiring, not the solenoid itself.
Related Fault Codes
Frequently Asked Questions
What does OBD2 code P0845 mean?
OBD2 code P0845 refers to Transmission Fluid Pressure Sensor/Switch B Circuit. If your code reader dashboard displays the generic DTC error code P0845, your vehicle is currently experiencing an active failure related to "Transmission Fluid Pressure Sensor/Switch B Circuit". Proper system troubleshooting is required to safely clear this warning.
What are the most common symptoms of DTC P0845?
Drivers experiencing code P0845 typically report: Check engine light, harsh downshifts, transmission shudder.
Is it safe to drive with trouble code P0845 active?
Driving with an active P0845 fault risks accelerating damage to failed tfp sensor b and related components. The longer the fault persists, the more expensive the eventual repair becomes — what starts as a sensor or solenoid issue can escalate to major mechanical failure.
How much does it cost to fix code P0845?
The estimated repair cost for P0845 ranges from $150 to $900 USD. Sensor replacement: $200 - $500; Valve body: $600 - $900
Sensor replacement: $200 - $500; Valve body: $600 - $900
Need Professional Diagnostic Assistance?
Always verify sensor signals and wiring integrity with an OBD2 scanner before purchasing replacement parts.
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