P0849 OBD-II Trouble Code: Transmission Fluid Pressure Sensor/Switch B Circuit Intermittent

Our certified mechanics come to you · Get a fair and transparent estimate upfront

Red-stars EXCELLENT RATING ON

Cost of diagnosing the P0849 code

P0849 is a diagnostic trouble code (DTC) for "Transmission Fluid Pressure Sensor/Switch B Circuit Intermittent". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$20.00
Toyota$20.00
BMW$20.00
SCHEDULE P0849 DIAGNOSTIC Get a fair and transparent estimate upfront

P0849 code definition

The P0849 code identifies a problem with fluid levels within the transmission. The powertrain control module controls a number of internal components within an automatic transmission, and the same control module is capable of detecting this fault. If the pressure at the pump within the transmission is not at the level required by factory specifications, then it will store a code via the powertrain control module.

What the P0849 code means

P0849 is the OBD-II generic code for a fault involving the pressure of fluid within an automatic transmission. The fluid inside of the transmission is responsible for tasks such as shifting into and out of gear, along with controlling the lockup of the torque converter. Pressure is maintained by a pump that regulates the fluid pressure. All of these components are controlled by the powertrain control module. Throttle position, engine speed, vehicle speed, and engine load are used to calculate the proper gear for the transmission to operate in. Without proper fluid pressure, the transmission may not be able to do that job effectively.

What causes the P0849 code?

The P0849 code has a number of common causes:

  • Blockage within hydraulic lines inside of transmission
  • Faulty solenoid within transmission
  • Faulty sensors within the transmission
  • Fault or electrical short in the powertrain control module
  • Low transmission fluid
  • Dirty or contaminated transmission fluid
  • Mechanical failure of transmission internal parts

What are the symptoms of the P0849 code?

Since the P0849 code deals with a problem with fluid levels in the transmission, there are a number of symptoms that accompany its appearance that are noticeable to the driver. If the vehicle has a warning light on the dashboard that is specifically intended to warn the driver of transmission issues, then this light should illuminate as soon as the required pump pressure within the transmission is not detected. After a few more instances of this fault, the Check Engine light should illuminate.

Physical symptoms such as rough shifting and slipping within the transmission will also accompany this fault. In severe cases, the transmission temperature may increase dangerously and fuel economy may suffer.

How does a mechanic diagnose the P0849 code?

The P0849 code will be diagnosed by a certified technician using an OBD-II scanner that is capable of retrieving the factory readings from the vehicle. The mechanic will view the fault code and see when it originally occurred. Then, the code will be reset and the vehicle will be taken for a test drive. If the code appears once again during this test drive, then the technician can confirm that the problem is not intermittent.

To test the electrical components around the circuits controlling the automatic transmission, the technician will then use a voltmeter to test various points around the circuit to confirm that proper amounts of power are flowing through the circuits. After all of that has been completed, the technician will check the transmission fluid itself. Low, contaminated, or old transmission fluid can cause the P0849 code to appear.

Common mistakes when diagnosing the P0849 code

Often the P0849 code is interpreted as a serious problem within the automatic transmission. While this may be true, it is just as likely that the problem is either electrical or due entirely to old, low, or dirty fluid in the transmission.

How serious is the P0849 code?

The P0849 code can range from moderately serious to very serious, depending on the root of the problem. If this code appears, it should certainly be diagnosed by a qualified technician promptly. In serious cases, there are parts within the transmission that need to be replaced before the vehicle can run properly once again. In moderate cases, the technician will simply have to add more fluid to the transmission. Having this problem addressed as soon as it appears it the best way to avoid costly major repairs down the road.

What repairs can fix the P0849 code?

The most common repairs to address the P0849 code are as follows:

  • Repair or replace wiring harness around transmission
  • Repair or replace powertrain control module
  • Repair or replace connections among wiring surrounding transmission or powertrain control module
  • Replace transmission fluid
  • Rebuild or replace automatic transmission

Additional comments for consideration regarding the P0849 code

The P0849 code can appear for a number of reasons relating to electrical issues or issues with the transmission fluid itself. Have the problem thoroughly diagnosed by a qualified technician prior to replacing any components in or around the transmission.

Need help with a P0849 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

trouble codes
P0849
OBD-II

No more waiting rooms! Our mechanics will come to you to diagnose and fix the P0849 code.

SCHEDULE P0849 DIAGNOSTIC
Get a $20 credit for the follow-up repair

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.8/5

Number of Reviews

5,583

Rating Summary
5,159
204
50
34
136
5,159
204
50
34
136

Matt

16 years of experience
35 reviews
Matt
16 years of experience
Jeep Compass - Check Engine Light is on Inspection - Holly Springs, North Carolina
Matt was awesome! Very knowledgeable, thorough. Really knows his stuff. Best part was his level of interaction and being able to ask him questions directly. You just don’t get that at the shops. Will definitely be using this service again and requesting Matt for all future jobs. Thanks again, Matt!

Matthew

32 years of experience
828 reviews
Matthew
32 years of experience
Land Rover LR2 - Check Engine Light is on - Hampton, Virginia
Matt is my go-to mechanic. Always professional and explains in detail what the problem is and how it’s being fixed. Highly recommend.

Richard

16 years of experience
115 reviews
Richard
16 years of experience
Honda Accord - Check Engine Light is on - San Ramon, California
Richard is Polite and skilled in inspecting the issues. I do recommend him for doing diagnostics before giving your car to the garage.

Michael

15 years of experience
565 reviews
Michael
15 years of experience
Chevrolet Avalanche 1500 - Check Engine Light is on - Marietta, Georgia
What professional handled himself well understood what was wrong with the car corrected it immediately and was on time


More related articles

P0848 OBD-II Trouble Code: Transmission Fluid Pressure Sensor/Switch B Circuit High
P0848 means there is an issue with the transmission fluid sensor circuit, possibly due to a faulty sensor, low fluid level, or fluid contamination.
P3478 OBD-11 Trouble Code: Cylinder 10 Exhaust Valve Control Performance
What What the P3478 code means When starting your vehicle, and when the vehicle is operating under a heavy weight, the engine will work in V8 mode. But when driving conditions are light, the engine will disable 4 of the...
P0346 OBD-II Trouble Code: Camshaft Position Sensor A Circuit Range/Performance (Bank 2)
P0346 P0346 code definition The appearance of the P0346 code indicates that the PCM has detected an incorrect voltage or waveform reading from the engine bank 2 camshaft sensor A camshaft position sensor circuit. What the P0346 code means The...

Related questions

eva PO597 engined coolant thermostat heater control circuit from obd diagnostic tool

Hi there. For the code P0597 to appear, there is an issue with the engine cooling system. Check the harness to the thermostat housing and a good connection and make sure that there is corrosion. Check for any coolant leaks...

Does the OBD system use more than lights to communicate with the driver?

Malfunction Indicator Lamps (MIL) and audible alarms are currently the only means by which the On-Board Diagnostics (OBD) system can inform the driver of any issues that adversely affect the operation of the engine or other electronically controlled system. The...

Ecu problem wanting to make sure

You need to have some of the codes like the first three diagnosed using the proper pinpoint tests until a problem is found. You may have an electrical harness short or a cut that is causing all the codes. Only...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com