P0843 on 2006-2010 Chevrolet Silverado: Transmission Pressure Sensor 'A' Circuit High Fixes

What's Unique About the 2006-2010 Chevrolet SILVERADO

The 2006-2010 Silverado generation is unique because it spans the transition from the 4-speed (4L60-E/4L80-E) to the 6-speed (6L80) automatic transmission. The cause and repair for P0843 are completely different depending on which transmission the truck has. On the 6-speed 6L80, the pressure switches are known to fail as they are fragile diaphragms integrated into the main control module (TEHCM) inside the pan. On the older 4-speeds, the issue is a more conventional, separate pressure switch manifold on the valve body.

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 GMT800 platform (sold as the 'Classic' in 2007) and the GMT900 platform (2007-2013). GMT800s typically have the 4-speed 4L60-E/4L80-E transmission. GMT900s are more likely to have the 6-speed 6L80, where the fix is different and more complex.

Symptoms You May Notice

• Harsh, abrupt, or violent shifting
• Transmission stuck in one gear ('limp mode')
• Check Engine Light or Service Engine Soon light is on
• No reverse gear engagement. [TSB #PIP4379K]
• "Range Inhibit" message may appear on the driver information center. [TSB #PIP4379K]
• Delayed or incorrect transmission shifting.
• Increased fuel consumption.

Most Likely Causes

1. Failed TFP Switch Diaphragm on TEHCM (6L80 Transmission) 🔴 High Probability The pressure switches on the 6L80 TEHCM are small rubber diaphragms that are a known weak point. They are exposed to constant heat and pressure cycles and are known to rupture or split over time, causing an open circuit.
   How to confirm: A technician will use a scan tool to monitor the voltage for TFP Switch 'A'. If it is stuck high (e.g., 5V) regardless of gear, the TEHCM is removed and the diaphragms are inspected for physical damage like tears or ruptures.
   Typical fix: Drop the transmission pan, remove the TEHCM, and replace the failed diaphragms using a specialized repair kit. 🎬 Watch: How to reseal the 6L80 pressure switches yourself. Some shops may opt to replace the entire TEHCM, which must then be programmed to the vehicle.
   Est. part cost: $50-$200 for a repair kit, $400-$800 for a remanufactured TEHCM.
2. Failed Transmission Fluid Pressure Switch Manifold (4L60-E/4L80-E Transmissions) 🔴 High Probability On the 4-speed transmissions, this manifold contains multiple pressure switches in one unit. It sits inside the hot transmission fluid, and the plastic and internal electronics can degrade and fail over time, causing an open or shorted circuit.
   How to confirm: After confirming external wiring is intact, a scan tool will show the pressure switch 'A' data stuck in a high voltage state. The part is located on the valve body inside the transmission pan and is the primary suspect.
   Typical fix: Drop the transmission pan, remove the valve body bolts securing the manifold, and replace the entire pressure switch manifold assembly. 🎬 Watch: Step-by-step guide to changing the 4L60-E pressure switch. It is best practice to also replace the internal wiring harness at the same time, as it has been subjected to the same heat cycles.
   Est. part cost: $35-$70 for the manifold switch.
3. Damaged Wiring or Poor Connection ⚪ Low Probability The wiring harness, both internal and external, can become brittle from heat and vibration, leading to cracks, shorts, or poor connections at the main transmission connector or at the TEHCM/PSM connector. The external harness is also susceptible to melting on nearby exhaust components.
   How to confirm: Visually inspect the external transmission harness. Use a multimeter to check for continuity, shorts to power, or shorts to ground on the signal wire between the TCM and the transmission connector.
   Typical fix: Repair the damaged section of the wiring harness or replace a corroded connector.
   Est. part cost: $10-$150 depending on whether a simple wire repair or a new harness is needed.

Rare But Worth Checking

• Faulty Transmission Control Module (TCM): This is rare. The TCM should only be considered after all other possibilities, including the sensor and wiring, have been definitively ruled out. A failed driver circuit within the module can cause a false high voltage reading.
• Torn Torque Converter O-Ring (4T45-E): While not directly applicable to the Silverado's RWD transmissions, GM TSB #08-07-30-018 for FWD vehicles shows a pattern where a torn torque converter O-ring can cause P0843 under specific light load conditions on an incline. This highlights that in rare cases, a hydraulic issue can manifest as this electrical code.

Diagnosis Steps

1. Connect a professional scan tool to read the trouble codes and check for any other related transmission codes. Note P0700 is expected.
2. Use the scan tool to monitor the live data stream for 'TFP Sensor/Switch A'. Check if the voltage is stuck high (typically at 5 volts) and does not change when commanding gears.
3. Inspect the transmission fluid level and condition. While unlikely to cause a 'Circuit High' fault, low or burnt fluid indicates other potential problems.
4. Visually inspect the external transmission wiring harness and the main connector for any signs of damage, corrosion, fluid intrusion, or melting on exhaust pipes.
5. If external wiring appears okay, drop the transmission oil pan to gain access to the internal components. This is a messy job, be prepared.
6. For 6L80 transmissions, remove the TEHCM and visually inspect the five pressure switch diaphragms for tears, ruptures, or dislodged seals. The damaged one 🎬 See how to rebuild and test the 6L80 TEHCM circuits. is often obvious.
7. For 4L60-E/4L80-E transmissions, inspect the pressure switch manifold and its connector for any visible damage, cracks, or discoloration from heat.
8. If no visible damage is found on the internal components, perform continuity and resistance checks on the internal wiring harness before replacing parts. The harness can become brittle and fail.

Parts You'll Likely Need

• Transmission Pressure Switch Repair Kit (for 6L80) — This is the most common and cost-effective fix for the 6L80 transmission. It addresses the known failure point of the TEHCM diaphragms without requiring replacement of the entire expensive module.
  Trusted brands: Sonnax (offers various kits like the Zip Kit 6L45-6L90-ZIP), TransGo (e.g., PSR-5 kit), ACDelco (often requires full TEHCM)
  OEM price range: $400-$800 (for full TEHCM, e.g., P/N 24256861)
  Aftermarket price range: $50-$200 (for repair kit)
• Transmission Fluid Pressure Switch Manifold (for 4L60-E/4L80-E Transmissions) (OEM #24229854 (for 4L80-E), 24229843 (for 4L60-E/4L65-E)) — This is the most common part to fail on the 4-speed transmissions, causing this code. It contains all the pressure switches in one assembly.
  Trusted brands: ACDelco, Rostra, Dorman
  OEM price range: $45-$70
  Aftermarket price range: $35-$55
• Automatic Transmission Fluid (DEXRON VI) (OEM #10-9395) — The transmission fluid must be drained to access the internal components and should be replaced with fresh, correct-spec fluid during the repair. A typical pan drop requires 5-7 quarts.
  Trusted brands: ACDelco, Valvoline, Castrol
  OEM price range: $8-$12 per quart
  Aftermarket price range: $7-$10 per quart

Related Codes That Often Appear With This One

• P0700 — This is a generic code that simply means the Transmission Control Module (TCM) has stored a fault and requested the Check Engine Light to be turned on. It will almost always be present with P0843.
• P0842, P0872, P0877, P0989 — These are other pressure switch circuit codes for the 6L80 transmission (Circuit Low/High for switches A, C, D, E). It is common for multiple switch diaphragms on the TEHCM to fail around the same time, triggering a group of these codes together.
• P0751, P0776 — These are shift solenoid performance codes. Since the solenoids and pressure switches are part of the same TEHCM assembly on the 6L80, a failing module can trigger both pressure and solenoid faults simultaneously.

Technical Service Bulletins (TSBs) & Recalls

• PIP4379K: Mentions P0843 as one of several DTCs that can cause a no reverse condition or a 'Range Inhibit' message, pointing towards an internal electronic or hydraulic fault. It advises diagnosing P0701 first if present.
• 08-07-30-018: Although for a FWD 4T45-E transmission, this TSB is notable. It documents cases where P0843 is set due to a torn torque converter O-ring causing intermittent TCC apply/release under light load. This is a rare mechanical cause for an electrical code.

Platform-Specific Known Issues

• Real-World Repair Story: 6L80 TEHCM Failure: A user on a Corvette Forum with a 6L80 transmission experienced limp mode and multiple pressure switch codes. The ultimate fix was replacing the entire TEHCM assembly and having it programmed to the vehicle's VIN, confirming this is the standard, albeit expensive, dealer-level repair for this issue.
• DIY Tip for 4-Speed Manifold Switch: A YouTube video focusing on 4L60E service highlights that the pressure switch manifold can accumulate fine metallic debris on the switch screens. While not always the cause of a 'Circuit High' fault, cleaning this debris during a service can extend the life of the component and prevent future issues.

Mechanic-Grade Diagnostic Values

• TFP Sensor/Switch 'A' Signal Voltage — expected: Typically 0.5V to 4.5V, changing with gear selection and load.. Failure: A sustained reading above 4.5V, often stuck at 5.0V, indicates a 'Circuit High' fault.
• Sensor Reference Voltage (Vref) at Connector — expected: Approximately 5.0V from the TCM/PCM.. Failure: Significantly lower or higher voltage indicates a problem with the TCM or wiring, not the sensor.
• Sensor Ground Circuit at Connector — expected: Near 0.0V.. Failure: Any significant voltage reading on the ground pin indicates a bad ground connection, which can cause a floating voltage and trigger a high circuit code.
• 4L60-E Pressure Control (PC) Solenoid Resistance — expected: 3.5 - 8.0 Ohms.. Failure: Readings outside this range indicate a failed solenoid, which is a separate component from the pressure switch manifold on this transmission.

Scan Tool Commands That Help

• GDS2 / Techline Connect: SPS (Service Programming System) — This is mandatory after replacing the TEHCM on a 6L80 transmission. The new module must be programmed with the vehicle's specific VIN and software calibration before it will function.
• GDS2 / Tech 2: Fast Learn / Reset Adapts — After TEHCM programming is complete, this procedure should be performed to reset the transmission's adaptive learn values, ensuring smooth shifting with the new components.
• Professional Scan Tool: Jumper Wire Test Verification — When testing wiring, a technician can jump the signal wire in the harness connector to a ground. A scan tool should show the code change from P0843 (Circuit High) to a 'Circuit Low' code (like P0842), which confirms the wiring and TCM are good and the sensor itself is the problem.

Wiring & Ground Locations

• 4L60-E Connector Pin N — On the main round transmission case connector.. This is the pin for Pressure Switch 'A' on 4L60-E transmissions up to 2008. A voltage test at this pin can help determine if the fault is internal or external to the transmission.
• 6L80 Main Connector (16-pin) — On the passenger side of the 6L80 transmission case. It is a twist-lock connector.. This is the sole electrical interface to the internal TEHCM. A poor connection here can cause P0843 and other communication codes. It's common for this connector to not be fully seated, which can be verified by ensuring the locking tab is engaged.
• 6L80 Connector Pins 10 & 11 — Within the 16-pin main transmission connector.. These are the CAN Bus Hi and Low communication wires. While not directly the TFP circuit, a fault here can disrupt all signals from the TEHCM, potentially leading to various codes including P0843.
• G105 / Engine Block Ground — Main ground point for the TCM, located on the engine block just above the upper oil pan.. A loose or corroded ground at this location can cause a floating ground for the TCM, leading to erratic sensor readings and false high circuit codes like P0843.

Real Owner Repair Stories

• YouTube channel 'Fix It Rich' (2008 GMC Denali with 6.2L engine and 6L80 transmission) — Multiple pressure switch codes and shifting problems.
  ✅ What actually fixed it The TEHCM was removed and inspected. All of the pressure switch membranes were found to be torn. The video demonstrates the process of removing the old torn films and replacing them with a new repair kit, which resolved the issue.
• Reddit user in r/MechanicAdvice (2009 Chevrolet Silverado 1500 with 4-speed automatic) — Bought the truck used, and on the second day of ownership it started shifting hard from 1st to 2nd gear and the check engine light came on.
  ❌ Tried (didn't work) The user was concerned it was a major transmission failure requiring a rebuild.
  ✅ What actually fixed it While the final repair isn't posted by the original author, the symptoms are classic for a pressure switch or solenoid failure on the 4-speed, which is a much less severe repair than a full rebuild. The abrupt onset of the problem after purchase is typical for these electronic failures.

OEM Part Supersession History

• 24241350 / 24252114 → 24256861 — Improved solenoids and an updated pressure manifold gasket to address common failure points.
  Heads up: TEHCMs from different year groups (e.g., a 2011+ module in a 2008 truck) are often not cross-compatible due to logic and calibration changes. The vehicle may go into limp mode or fail to communicate if the wrong year TEHCM is installed, even if it physically fits. Always match the part number or use a compatible superseded number.
• 24256861 → 19435614 — Standard part number lifecycle update by GM.

Model Year Variations Within This Range

• 2009+: For the 4L60-E/4L65-E/4L70-E family, the 2009 model year saw a significant change. The internal wiring harness, pin-out, and internal mode switch were changed, and the external Park/Neutral Position switch was eliminated. This means the pressure switch manifold and internal harness from a 2006-2008 model will not work in a 2009+ 4-speed model.
• 2006-2009 vs 2010-2013 (6L80): Early 6L80 TEHCMs (e.g., P/N 24252114) are known to be more prone to pressure switch failures. Later models (e.g., P/N 24256861) featured improved solenoids and gaskets, though the diaphragm design remained a weak point.