P0843 Transmission fluid pressure sensor/switch A circuit, high input

Transmission fluid pressure sensor/switch A, high input

Severity not verified — if the car runs badly, have it inspected

We found no source that rates how serious P0843 is on its own.

Source: how we rate severity

P0843 in short

P0843 means the transmission computer sees a very high signal from fluid pressure sensor or switch A. A short to positive voltage, wiring, a failed sensor or the module can cause it. General Motors links it to false codes and harsh shifts on some trucks, so have a shop check it.

The transmission fluid pressure sensor or switch reports hydraulic pressure to the computer. A high-input code means the signal is above the expected range, which points to the circuit or the sensor as much as to real pressure.

TroubleCodes.net lists wiring, a short to positive voltage, the sensor and the module. General Motors published a bulletin on checking the pressure switch for false codes including P0843 on 6T70, 6T75, 6L50, 6L80 and 6L90 transmissions.

Another GM bulletin covers harsh shifts into third or fifth on some 2010 vehicles with 6T70 or 6T75 transmissions, where P0843 may be stored in the module.

Most likely causes

  1. Wiring fault or short to voltage in the circuit

    Common general cause
    Why it ranks here
    TroubleCodes.net lists wiring and a short to positive voltage.
    What would change this
    Rises if the harness is chafed or the connector is corroded.

  2. Failed or false-reading pressure switch

    Common general cause
    Why it ranks here
    TroubleCodes.net lists the sensor, and GM publishes a check for false codes from the switch.
    What would change this
    Rises if the wiring tests good and the shifts are normal.

  3. Harsh shift on 6T70/6T75 built 4/1/10 to 5/8/10

    Supported by vehicle data
    Why it ranks here
    GM PI0179 says P0843 may be stored with a harsh shift into third or fifth on these 2010 vehicles.
    What would change this
    Rises on a covered vehicle with harsh shifts.

  4. Transmission control module

    Possible — needs testing
    Why it ranks here
    TroubleCodes.net lists the module.
    What would change this
    Rises only after the switch and wiring are ruled out.
    How to test the transmission control module (tcm)

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read codes from the engine and transmission modules with a scan tool that supports both, before anything is cleared. Note P0842, P0841 and any harsh-shift complaint.

    Low riskTool: scan tool that reads the transmission module

  2. Inspect the pressure switch connector and harness for chafing, corrosion and fluid inside the plug.

    Low risk

  3. Have a shop check the pressure switch state against the maker's procedure; GM has a switch check for false codes.

    Best left to a shopTool: scan tool and multimeter

    Warning:Shop test. It needs the maker's specifications.

Symptoms

  • Check engine light
  • Harsh shift into third or fifth on some GM cars
  • Limp mode Gets more serious: stop and have it checked.

How to fix

  1. Do not clear the code before the transmission module has been read.

  2. Ask a dealer whether your VIN has an open bulletin. General Motors has published two that name this code.

Parts and cost context

  • Transmission control module (TCM):Do not replace the module for P0843 unless tests point to it.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Chevrolet

  • 2006–2007 · Silverado 1500

    Supported by vehicle data

    6T70, 6T75, 6L50, 6L80 and 6L90 automatics: information on checking the transmission fluid pressure switch for false codes P0842, P0843, P0872, P0873, P0877, P0878, P0989 or P0990. Whether the bulletin is still current is not verified.

  • 2010 · Equinox

    Supported by vehicle data

    2010 vehicles with 6T70 or 6T75 built 4/1/10 to 5/8/10: harsh shift typically into third or fifth gear, and the technician may find P0843 stored in the TCM as active or history. Whether the bulletin is still current is not verified.

  • 070730015Status unverified

    GM 07-07-30-015: TFP switch check for false codes including P0843

    2006–2007silverado-1500 · NHTSA 10021845

    6T70, 6T75, 6L50, 6L80 and 6L90 automatics: information on checking the transmission fluid pressure switch for false codes P0842, P0843, P0872, P0873, P0877, P0878, P0989 or P0990.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • PI-0179Status unverified

    GM PI0179: harsh shift into third or fifth, P0843 in the TCM

    2010equinox · NHTSA 10036506

    2010 vehicles with 6T70 or 6T75 built 4/1/10 to 5/8/10: harsh shift typically into third or fifth gear, and the technician may find P0843 stored in the TCM as active or history.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

GMC

  • 2007 · Yukon

    Supported by vehicle data

    6T70, 6T75, 6L50, 6L80 and 6L90 automatics: information on checking the transmission fluid pressure switch for false codes P0842, P0843, P0872, P0873, P0877, P0878, P0989 or P0990. Whether the bulletin is still current is not verified.

  • 2010 · Acadia

    Supported by vehicle data

    2010 vehicles with 6T70 or 6T75 built 4/1/10 to 5/8/10: harsh shift typically into third or fifth gear, and the technician may find P0843 stored in the TCM as active or history. Whether the bulletin is still current is not verified.

  • 2010 · Terrain

    Supported by vehicle data

    2010 vehicles with 6T70 or 6T75 built 4/1/10 to 5/8/10: harsh shift typically into third or fifth gear, and the technician may find P0843 stored in the TCM as active or history. Whether the bulletin is still current is not verified.

  • 070730015 (Gmc)Status unverified

    GM 07-07-30-015: TFP switch check for false codes including P0843

    2007yukon · NHTSA 10021845

    6T70, 6T75, 6L50, 6L80 and 6L90 automatics: information on checking the transmission fluid pressure switch for false codes P0842, P0843, P0872, P0873, P0877, P0878, P0989 or P0990.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • PI-0179 (Gmc)Status unverified

    GM PI0179: harsh shift into third or fifth, P0843 in the TCM

    2010acadia, terrain · NHTSA 10036506

    2010 vehicles with 6T70 or 6T75 built 4/1/10 to 5/8/10: harsh shift typically into third or fifth gear, and the technician may find P0843 stored in the TCM as active or history.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Buick

  • 2010 · Enclave

    Supported by vehicle data

    2010 vehicles with 6T70 or 6T75 built 4/1/10 to 5/8/10: harsh shift typically into third or fifth gear, and the technician may find P0843 stored in the TCM as active or history. Whether the bulletin is still current is not verified.

  • 2010 · LaCrosse

    Supported by vehicle data

    2010 vehicles with 6T70 or 6T75 built 4/1/10 to 5/8/10: harsh shift typically into third or fifth gear, and the technician may find P0843 stored in the TCM as active or history. Whether the bulletin is still current is not verified.

  • PI-0179 (Buick)Status unverified

    GM PI0179: harsh shift into third or fifth, P0843 in the TCM

    2010enclave, lacrosse · NHTSA 10036506

    2010 vehicles with 6T70 or 6T75 built 4/1/10 to 5/8/10: harsh shift typically into third or fifth gear, and the technician may find P0843 stored in the TCM as active or history.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Cadillac

  • 2010 · SRX

    Supported by vehicle data

    2010 vehicles with 6T70 or 6T75 built 4/1/10 to 5/8/10: harsh shift typically into third or fifth gear, and the technician may find P0843 stored in the TCM as active or history. Whether the bulletin is still current is not verified.

  • PI-0179 (Cadillac)Status unverified

    GM PI0179: harsh shift into third or fifth, P0843 in the TCM

    2010srx · NHTSA 10036506

    2010 vehicles with 6T70 or 6T75 built 4/1/10 to 5/8/10: harsh shift typically into third or fifth gear, and the technician may find P0843 stored in the TCM as active or history.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • P0841Transmission fluid pressure sensor or switch reading does not make sense

    Shares causes Possible — needs testing

    P0841 is the range or performance fault on the same pressure sensor or switch circuit.

All Transmission codes

P0843 questions

What does high input mean?

The sensor signal is higher than the computer expects. That can come from a short to voltage, the sensor, or the module, not only from real pressure.

Is P0843 serious?

We found no source that rates it. Have a shop read the transmission module, especially if shifts are harsh.

Sources and review

  1. P0843 Trouble Code: Transmission fluid pressure sensor/switch A, high input — TroubleCodes.net
  2. GM 07-07-30-015: TFP switch check for false codes including P0843 — General Motors
  3. GM PI0179: harsh shift into third or fifth, P0843 in the TCM — General Motors
Last reviewed
Written by
Saurabh K.
Editorial review
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Technician review
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