Code Definition

P1843 — 1-2 Shift Solenoid circuit high input

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: GM

About P1843

P1843 is a manufacturer-specific powertrain diagnostic trouble code recorded for GM vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1843 is stored, the module has detected a signal or supply voltage higher than the expected operating range.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

P1843 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

This DTC sets when the Transmission Control Module (TCM) detects that the voltage on the 1 to 2 shift solenoid control circuit is abnormally high, typically indicating an open circuit or a short to battery voltage. The 1 to 2 shift solenoid directs hydraulic pressure during the shift from first to second gear. A high control circuit signal prevents proper solenoid activation, which can cause incorrect shift timing, failure to upshift, or the transmission defaulting to a fail safe gear. The fault usually lies in an open solenoid winding, a break in the control wiring, or a feed of voltage into ...

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