P0848 on 2006-2013 Chevrolet Silverado 1500: Transmission Pressure Switch 'B' Circuit High Fixes

What's Unique About the 2006-2013 Chevrolet SILVERADO 1500

The 2006-2013 Silverado 1500 spans two generations and commonly used two different automatic transmissions, which affects the repair. Early models (2006-2008) often have the 4-speed 4L60-E, where the pressure switches are part of a replaceable manifold inside the oil pan. Later models (2009-2013) frequently use the 6-speed 6L80, which integrates the pressure switches, solenoids, and TCM into a single, more complex unit called the Transmission Electro-Hydraulic Control Module (TEHCM). Failures in the 6L80's TEHCM are very common and almost always require replacing the entire assembly, which must then be programmed to the vehicle's VIN.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Generation note: This range covers the end of the first generation (GMT800, 'Classic' models up to 2007) and the entire second generation (GMT900, 2007-2013). The GMT800s primarily used the 4L60-E/4L65-E transmissions, where the fix is typically a pressure switch manifold. The GMT900s transitioned to the 6L80 6-speed automatic, where the fix is almost always a new TEHCM.

Symptoms You May Notice

• Harsh, erratic, or delayed shifting.
• Transmission getting stuck in one gear (limp mode).
• Check Engine Light or Transmission Warning Light is on.
• "Shift Inhibited" message on the driver information center.
• Reduced fuel economy.
• Transmission slipping or failing to engage.
• Torque converter clutch may fail to engage or disengage properly.

Most Likely Causes

1. Faulty Transmission Electro-Hydraulic Control Module (TEHCM) 🔴 High Probability → Shop Transmission Assembly On 6L80 transmissions, the pressure switches are integrated into the TEHCM, a component known for high failure rates. Heat and vibration cause internal electronic faults and cracks in the laminate pressure switch membranes, leading to high voltage readings.
   How to confirm: After dropping the transmission pan, the component can be visually inspected. Multiple pressure sensor codes (e.g., P0843, P0873) are a very strong indicator of TEHCM failure. Diagnosis is confirmed by replacing the unit.
   Typical fix: Replace the entire TEHCM assembly. The new TEHCM must be programmed to the vehicle's VIN using dealership-level software.
   Est. part cost: $300-$600
2. Faulty Transmission Fluid Pressure (TFP) Switch Manifold 🔴 High Probability → Shop Transmission Assembly On 4L60-E models, the plastic pressure switch manifold is submerged in hot fluid, causing the plastic and internal diaphragms to become brittle, crack, and fail, leading to fluid leaks or electrical faults.
   How to confirm: After dropping the transmission pan, the manifold can be visually inspected for cracks. Testing continuity across the switch pins with a multimeter can confirm an electrical fault. Often, the seals between the manifold and valve body degrade, causing pressure loss.
   Typical fix: Replace the pressure switch manifold. It is recommended to replace the internal wiring harness 🎬 Watch: How to change the pressure switch on a 4L60-E at the same time as a preventative measure.
   Est. part cost: $50-$150
3. Internal Transmission Wiring Harness Failure 🟡 Medium Probability → Shop Transmission Assembly The wiring harness inside the transmission is constantly submerged in hot fluid, which can cause the insulation to become brittle, crack, and short circuit over time, especially at the connector pins.
   How to confirm: With the transmission pan removed, visually inspect the wiring harness leading to the pressure switch manifold or TEHCM for signs of cracked insulation, exposed wires, or corrosion at the connector.
   Typical fix: Replace the internal transmission wiring harness.
   Est. part cost: $50-$150
4. Low or Contaminated Transmission Fluid ⚪ Low Probability → Shop Transmission Assembly Neglecting fluid service can lead to fluid breakdown and sludge buildup, which can interfere with the proper mechanical and electrical operation of sensors and solenoids.
   How to confirm: Check the transmission fluid level and condition using the dipstick. Fluid should be bright red and clear, not dark brown, black, or smell burnt.
   Typical fix: Perform a transmission fluid and filter change. If the fluid is heavily contaminated with clutch material, it may indicate a more severe internal failure is imminent.
   Est. part cost: $75-$200

Rare But Worth Checking

• Poor TCM/Engine Ground Connection:

Diagnosis Steps

1. Check the transmission fluid level and condition. Correct any low or burnt fluid issues first.
2. Use a professional scan tool to read all transmission codes. Note if other pressure switch codes (P0843, P0873) or a general TCM code (P0700) are present.
3. Inspect the external transmission wiring harness and the main connector for any visible damage, corrosion, or fluid leaks.
4. Check for good power and ground connections at the TCM. On GMT900 models, check underhood fuses #14 and #19 for the TCM.
5. Safely raise the vehicle and drain the transmission fluid.
6. Remove the transmission oil pan to access the internal components.
7. Visually inspect the internal wiring, pressure switch manifold (4L60-E), or TEHCM (6L80) for obvious damage, cracks, or signs of overheating.
8. If the wiring and connections appear intact, the most likely cause is the pressure switch assembly itself. Replace the pressure switch manifold (4L60-E) or the entire TEHCM (6L80).
9. Install a new transmission filter and pan gasket.
10. Refill the transmission with the correct type and amount of new fluid (DEXRON-VI).
11. For 6L80 repairs, program the new TEHCM to the vehicle's VIN using appropriate scan tool software.
🎬 Watch: How to program a 6L80 unit for your truck
12. Clear the trouble codes with a scan tool and perform a test drive to ensure the shifting issues are resolved.

Parts You'll Likely Need

• Transmission Electro-Hydraulic Control Module (TEHCM) (OEM #24256861 (ACDelco)) — For models with the 6L80 6-speed transmission, this integrated unit contains the pressure switches and is the most common point of failure for code P0848. Replacement requires programming.
  Trusted brands: ACDelco (OEM), Dorman (Aftermarket, quality can be inconsistent)
  OEM price range: $350-$500
  Aftermarket price range: $250-$400
• Transmission Pressure Switch Manifold (OEM #24229843 (ACDelco)) — For models with the 4L60-E 4-speed transmission, this part contains all the pressure switches and is typically replaced as a single unit to fix a P0848 code.
  Trusted brands: ACDelco (OEM), Rostra, ATP
  OEM price range: $80-$150
  Aftermarket price range: $50-$100

Related Codes That Often Appear With This One

• P0700 — P0700 is a general fault code requested by the Transmission Control Module (TCM). It indicates that the TCM has stored a specific fault code, such as P0848, and has illuminated the Check Engine Light.
• P0843 — This code relates to Transmission Fluid Pressure Switch 'A' Circuit High. Seeing multiple pressure switch codes together strongly points to a failure of the common component they are part of, like the pressure switch manifold or TEHCM.
• P0873 — This code is for Transmission Fluid Pressure Switch 'C' Circuit High. Like P0843, its presence alongside P0848 suggests a larger component failure.
• P0756 — This code for 'Shift Solenoid 'B' Performance/Stuck Off' can appear with P0848. A service manual notes this combination may indicate an open circuit on the pressure switch 2 circuit or a stuck shift valve.

Technical Service Bulletins (TSBs) & Recalls

• PIP4379M: Mentions P0848 in a list of DTCs that can occur due to internal transmission issues and advises diagnosing general TCM code P0701 first if present.
• PIP5161: Discusses issues where a TEHCM may fail to program correctly, sometimes due to low battery voltage or incompatible software, resulting in the transmission being locked in limp mode.

Mechanic-Grade Diagnostic Values

• 6L80 TEHCM PWM Solenoid Resistance — expected: 3-8 Ohms. Failure: A reading outside this range indicates a failed solenoid within the TEHCM, requiring replacement of the entire module.
• 6L80 TEHCM On/Off Shift Solenoid Resistance — expected: 20-40 Ohms. Failure: Resistance outside this range points to a faulty shift solenoid inside the TEHCM.
• TFP Sensor Signal Voltage (Key On, Sensor Disconnected) — expected: Should be near 0V.. Failure: If voltage is present (e.g., 5V or 12V), it indicates a short to voltage in the wiring harness between the TCM and the transmission connector.
• TFP Sensor Reference Voltage (Key On, at sensor connector) — expected: Approximately 5V or 12V, depending on the specific transmission model.. Failure: An incorrect voltage suggests a problem with the TCM's power supply or an issue in the reference voltage wire.

Scan Tool Commands That Help

• GM Tech2 / GDS2: Transmission Data / Switch Status — For 4L60-E diagnostics, use this to view the live state (On/Off) of all pressure switches while manually shifting gears with the engine running. This can confirm if switch 'B' is stuck electrically high.
• GM Tech2 / GDS2: Solenoid Test / Output Overrides — For 6L80 diagnostics, this allows a technician to command each solenoid ON and OFF. When used with a special test plate (J-47825-1) and an air supply, you can physically check if valves are stroking correctly, helping to isolate a TEHCM failure.
• GM Tech2 / GDS2: Transmission Service Fast Learn — This procedure is critical after replacing a TEHCM on a 6L80 transmission. It allows the new module to learn the clutch fill times and pressure characteristics, preventing harsh shifts after the repair.
• GM Tech2 / GDS2: Solenoid Cleaning Process — If a solenoid performance DTC is present or a solenoid fails an air test, running this automated cleaning cycle can sometimes flush debris and restore function, potentially avoiding a TEHCM replacement.

Wiring & Ground Locations

• TCM Connector (80-way on 2009+) — The main connector for the Transmission Control Module, which is integrated into the TEHCM inside the transmission pan on 6L80 models.. For external wiring checks, Pin 17 (Pink wire) is often the signal circuit for Fluid Pressure Switch 1. Testing for a short-to-voltage on this wire is a key diagnostic step before dropping the pan.
• G101 — On GMT900 trucks, this ground is located on the lower left side of the radiator core support.. A poor connection at this major chassis ground can cause various electrical issues, including erratic sensor readings that could trigger a 'Circuit High' code.
• G103 — Located on the cowl in the left rear of the engine compartment, often near the brake booster on GMT900 models.. This is a critical ground point for the Body Control Module (BCM) and Instrument Panel Cluster. While not directly for the TCM, a poor connection here can cause communication errors or strange electrical behavior system-wide.

Real Owner Repair Stories

• eBay Buyer Feedback (Vehicle with 6L80 Transmission) — Unspecified transmission issues requiring a new TCM.
  ✅ What actually fixed it The owner purchased a pre-programmed TEHCM (part #24256861). After disconnecting the battery, installing the new part, and clearing codes, the truck was reported to be running well.

OEM Part Supersession History

• 24256861 → 19435614 — Part revision and update by the manufacturer.
  Heads up: The original part number 24256861 is a widely recognized TEHCM for 6L80 transmissions in this vehicle range. It has been superseded by newer numbers. It is critical to ensure the replacement TEHCM is programmed for the specific vehicle VIN.
• Multiple (e.g., 24248192, 24252318, 24253557) → Dorman 609-001 (Aftermarket) — Dorman offers a remanufactured alternative to several OEM TEHCM part numbers.
  Heads up: Dorman claims their remanufactured TEHCMs use upgraded materials like PEEK plastic to improve heat resistance. However, like the OEM part, it requires programming after installation. Customer reviews on aftermarket TEHCMs are mixed, with some reporting premature failures.

Model Year Variations Within This Range

• 2006-2010 (approx.): Early 6L80 TEHCM units are noted to be more prone to TCC (Torque Converter Clutch) apply solenoid failure and pressure switch membrane cracking under heat.
• 2011-2013 (approx.): Later TEHCM units featured improved solenoids, updated logic, and better thermal tolerance, though they are still a common failure item.