The OBD2 code P0848 indicates an issue with the “B” transmission fluid pressure sensor/switch circuit, suggesting that the sensor is sending a signal that is too high. This sensor plays a critical role in monitoring the hydraulic fluid pressure within the transmission, which is essential for proper gear selection and operation.
P0200 quick overview
| Meaning | P0848: Transmission Fluid Pressure Sensor/Switch “B” Circuit High |
| Is it serious? | Yes, it can affect the transmission’s ability to properly shift gears, potentially leading to noticeable driving issues. |
| Possible causes | – Faulty transmission fluid pressure sensor/switch – Wiring or connector issues in the sensor circuit – Transmission fluid level is incorrect or the fluid is contaminated – Transmission control module (TCM) problems |
| How to diagnose? | Check the transmission fluid level and quality; replace if dirty or incorrect level. Inspect the sensor and circuit wiring for damage or disconnections. Test the sensor’s functionality with a scan tool or multimeter. Consider TCM issues if no other faults are found, including checking for software updates or replacement. |
P0200 Meaning
Imagine your car’s transmission as a complex system that decides how and when to change gears for optimal driving. The Transmission Fluid Pressure Sensor, akin to a watchful guardian, monitors the pressure of the fluid that makes these gear changes smooth.
When the sensor signals that the pressure is too high, it’s like saying the fluid is pushing too hard, which can confuse the system and cause it to misbehave. This can lead to gear shifting problems, making the car feel sluggish or jerky when it tries to find the right gear.
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How to fix P0200 – learn from mechanics
I looked into P0200 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.
Case #1: GMC
Vehicle information 2001 GMC Savana 2500 5.0L
Issue + repair history
- Check engine light was on with codes P0200 and P0300 stored in ECM
- Engine running very rich, emitting unburned fuel odor
- Replaced fuel injectors as an assembly twice, but problem persisted
- Replaced coolant temp sensor
- Engine started acting up when hot, especially noticeable when idling
- Checked wiring harness, replaced coolant sensor, and unplugged O2 sensors with no improvement
- Issue identified as a problem with the computer harness going to the fuel injectors
- Replaced the electrical plug on the harness, resolving the issue
Other OBD2 Codes + Test Results
- P0300: Random misfire
- P0200: Fuel injector circuit
Mechanic suggestions
- Test fuel injector circuit from fuel injector connector to PCM
- Visually inspect PCM for water/fuel intrusion, massage wiring while testing fuel injector circuits
- Verify that none of the pins on top of the intake (injector bulkhead connector) are bent over
- Verify that each injector is receiving the correct signal from PCM, ensuring each has a constant 12-volt supply and PCM grounds the other side individually
- Check scan data and look at coolant temp sensor to ensure it’s reading accurately
- Flush injectors if necessary, inspect for any bent pins, and ensure proper signal from PCM
Final fix
- Identified a bent pin for cylinder number five and flushed the injectors, resolving the issue with cylinder number one still skipping after the flush.
Case #2: Chevrolet
Vehicle information 2002 Chevrolet Express 2500 LS 5.7L
Issue + repair history
- Intermittent P0200 code (injector driver malfunction)
- Hours of research yielded no solutions
- Discovered a rubbed-through section of wire in the main engine harness where it touched the transmission fill tube, specifically the blue-white wire for injector #8
- Repaired the harness, which required significant effort to get enough slack, but it can be done in about an hour
- Previous repairs included a new PCM and a fresh tune-up
Other OBD2 Codes + Test Results
- P0200: Injector driver malfunction
Mechanic suggestions
- If experiencing similar issues with other injector circuits, consider removing 3 inches of each harness to save costs, but be aware that issues may return
- Try rerouting the harness on the other side of the dipstick after unplugging the bulkhead connector to clear the AC lines
Final fix
- Located and repaired a rubbed-through section of wire in the main engine harness where it touched the transmission fill tube, specifically the blue-white wire for injector #8. Added protective tape to prevent future chafing. After repair, the issue was resolved.
Case #3: Chevrolet
Vehicle information 2001 Chevrolet Silverado 2500 6.0L
Issue + repair history
- Ran P0200 test, came up blank; not enough misfire count to pinpoint the issue
- At idle, showed a count of 2 misfires on cylinder #7 out of 8 cylinders
- All data looked good while driving, but history freeze frame showed bank 2 LT at 10% and bank 1 LT at 1%
- Discovered about 3 injectors out of spec but customer declined replacement as they couldn’t feel the engine miss at times
Other OBD2 Codes + Test Results
- P0200:
Mechanic suggestions
- Clean the injectors with GM Top Engine Cleaner mixed 50/50 with gas in an OTC injector cleaner
- Block off the PCV and check the crankcase for vacuum due to an intake manifold leak
- Test the amperage draw; if injectors are 12 ohms, draw should be approximately 1 amp per injector
- If possible, induce misfire with a vacuum gauge attached to check for fluttering, indicating sticky valves
- Consider the possibility of injectors becoming plugged on higher mileage engines due to fuel dead-end and dirt accumulation
- Check the connectors to the injectors for ‘fretting’ of the metal terminals; clean terminals and apply dielectric grease
Final fix
- Replacing 3 injectors out of spec fixed the issue
How to diagnose P0200
I made you an overview of solving this DTC, based on all the advice that was suggested by certified mechanics to address this issue in previously mentioned service cases.
| Diagnostic Step | Brief Explanation |
|---|---|
| Check transmission fluid | Ensure the fluid is at the correct level and not contaminated, as this can cause pressure issues. |
| Inspect wiring and connectors | Look for any signs of damage or loose connections that might affect the sensor’s readings. |
| Verify sensor functionality | Use diagnostic tools to check if the sensor is operating within its expected range. |
| Check for TCM updates or damage | Software updates or TCM faults can lead to incorrect sensor readings, requiring professional attention. |
These cases underscore the importance of accurate diagnostics, focusing on both the electrical components and the hydraulic system of the transmission. Correctly addressing the P0848 code involves checking the fluid pressure sensor and its circuit, ensuring the transmission fluid is in good condition, and considering the potential impact of TCM issues.
Car Diagnostics Training
- Car Electrical basics
- OBD-II scanner basics
- How to use an OBD reader
- Introduction to a Bi-directional Scan tool
- OBD scanner buyer’s guide + discounts
I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko