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P0849

Transmission Fluid Pressure Sensor/Switch B Circuit Intermittent

Transmission / hydraulics Generic OBD-II Medium

What it means

P0849 means the "B" transmission fluid pressure sensor/switch signal is cutting in and out intermittently. The controller uses this pressure reading to manage shift timing and quality, so a dropout can cause the occasional harsh or delayed shift and can briefly force a fail-safe mode. The engine starts and runs normally; the intermittent nature usually points to a marginal connection or a sensor that's beginning to fail.

Medium

Can I keep driving? Usually driveable, but expect occasional harsh or delayed shifts and brief limp mode; fix it before the fault becomes constant.

Common symptoms

What you'll notice

Common causes

Most likely first

  1. Intermittent wiring or connector fault (chafed wire, loose or corroded pin) in the sensor B circuit
  2. Failing transmission fluid pressure sensor/switch B
  3. Low or degraded transmission fluid
  4. Faulty transmission control module (less common)

How to diagnose & fix

Work through it in order

  1. Read freeze-frame data and note the conditions when the code sets.
  2. Wiggle-test the sensor connector and harness while watching live pressure data for dropouts.
  3. Check the transmission fluid level and condition.
  4. Repair the intermittent wiring; replace the pressure sensor/switch if its signal drops out.
  5. Clear the code and road-test to confirm the fix.

FAQ

Quick answers

Is it safe to drive with P0849?+
For short trips usually yes, but an intermittent pressure signal can trigger harsh shifts or a temporary limp mode. Repair it before it becomes a permanent fault.
Can I just clear P0849?+
You can, and it may stay away briefly because the fault is intermittent, but it returns until the wiring or sensor is fixed.

Related codes

Often seen with P0849

P0845Transmission Fluid Pressure Sensor/Switch P0846Transmission Fluid Pressure Sensor/Switch P0847Transmission Fluid Pressure Sensor/Switch P0848Transmission Fluid Pressure Sensor/Switch

Read & clear P0849 yourself

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✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX