Wiring fault on the 1-2 shift solenoid circuit, such as an open circuit, chafed wire or short to voltage; Corroded, damaged or loose connector at the solenoid, the transmission internal harness pass-through or the control module; Faulty 1-2 shift solenoid with an open internal winding; Damaged internal transmission wiring harness; Low or contaminated transmission fluid affecting the solenoid or its connector; Faulty transmission control module driver circuit; Outdated control module calibration, where a known update exists for the model and year.

P1843

1-2 Shift Solenoid Circuit High Voltage.

Cadillac
Powertrain
Manufacturer code
Medium severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
8: AreaTransmission
43: FaultThe specific fault in that area

What it means

P1843 on a Cadillac means the transmission control module has detected a high voltage on the 1-2 shift solenoid circuit. The module monitors the voltage on the solenoid driver circuit and sets the code when the reading is higher than expected for the commanded state. This usually points to an open circuit, a short to voltage or a fault in the solenoid or control module.

Symptoms

Malfunction indicator lamp or transmission warning lamp on
Harsh, delayed or missed 1-2 shift
Transmission stuck in one gear or in a limp-home mode
Poor acceleration or the engine revving high before upshifting
Reduced fuel economy
Gearbox may not shift correctly between other gears

Possible causes

Wiring fault on the 1-2 shift solenoid circuit, such as an open circuit, chafed wire or short to voltagelikely
Corroded, damaged or loose connector at the solenoid, the transmission internal harness pass-through or the control modulelikely
Faulty 1-2 shift solenoid with an open internal windinglikely
Damaged internal transmission wiring harnesspossible
Low or contaminated transmission fluid affecting the solenoid or its connectorpossible
Faulty transmission control module driver circuitrare
Outdated control module calibration, where a known update exists for the model and yearrare

How to diagnose

Read all stored and pending codes and record the freeze frame data, noting whether other solenoid or transmission codes are present
Check the transmission fluid level and condition, following the procedure for the specific transmission fitted
Inspect the wiring and connectors between the transmission and the control module for chafing, corrosion, bent pins and fluid contamination
Check the transmission case connector for fluid ingress, as it can wick up the harness
Measure the 1-2 shift solenoid resistance and compare it with the specification for the model and transmission
Check the circuit for continuity, short to voltage and short to earth with the control module disconnected, using the wiring diagram for the vehicle
Check the supply voltage and earth connections to the control module and the battery condition
Check for any applicable calibration updates or technical bulletins for the model before suspecting the control module

How to fix

Repair or replace damaged wiring or connectors on the solenoid circuit
Clean or replace a corroded or fluid-contaminated connector or terminal
Replace the 1-2 shift solenoid, or the solenoid assembly where it is not sold separately, if it fails the resistance test
Replace the internal transmission harness if it is found to be faulty
Correct the fluid level or replace the fluid and filter if it is contaminated, as the manufacturer specifies
Replace or reprogram the transmission control module only after the wiring and solenoid are proven good, or if an update is known to apply

Can I keep driving?

Medium severity

The car can usually be driven carefully for a short time, but poor shifting or limp mode can strain the transmission. Have it diagnosed soon and avoid heavy loads or towing until it is repaired.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.