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Engine-Codes – Generic – P1843

P1843 Code - 1-2 Shift Solenoid Circuit High Input Voltage

Quick Answer

The P1843 diagnostic trouble code (DTC) indicates a problem with the 1-2 shift solenoid circuit in the transmission. Common causes include Wiring harness issues or shorts in the 1-2 shift solenoid circuit, Faulty 1-2 shift solenoid, Malfunctioning transmission control module (TCM). Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P1843 indicates 1-2 Shift Solenoid Circuit High Input Voltage.
Common causes
Common causes include Wiring harness issues or shorts in the 1-2 shift solenoid circuit, Faulty 1-2 shift solenoid, Malfunctioning transmission control module (TCM).
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
What is this?
Table of contents Created and updated by William Orellana on Sep 08, 2024
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Code P1843 Description

The P1843 diagnostic trouble code (DTC) indicates a problem with the 1-2 shift solenoid circuit in the transmission. The transmission control module (TCM) monitors the voltage levels in the solenoid circuit, and if it detects that the input voltage is too high, it will trigger this code. The 1-2 shift solenoid is responsible for controlling the hydraulic pressure that engages the 1st and 2nd gear in the transmission. When the input voltage is high, it can lead to improper shifting, harsh shifting, or even failure to shift between these gears.

OBDII Code P1843 - 1-2 Shift Solenoid Circuit High Input Voltage
P1843 Code - 1-2 Shift Solenoid Circuit High Input Voltage

Common Causes of P1843

  1. Wiring harness issues or shorts in the 1-2 shift solenoid circuit
  2. Faulty 1-2 shift solenoid
  3. Malfunctioning transmission control module (TCM)
  4. Low transmission fluid level or poor-quality fluid
  5. Electrical issues such as a blown fuse or faulty connectors

Symptoms of P1843

  1. Erratic or delayed shifting between 1st and 2nd gears
  2. Harsh or rough shifting
  3. Poor acceleration
  4. Decreased fuel efficiency
  5. Transmission slipping

How to Fix P1843

  1. Diagnose the issue by using a scan tool to retrieve the trouble codes and monitor the voltage levels in the 1-2 shift solenoid circuit.
  2. Inspect the wiring harness for any damage, shorts, or loose connections. Repair or replace any faulty wiring.
  3. Test the 1-2 shift solenoid for proper operation. Replace the solenoid if it is found to be faulty.
  4. Check the transmission control module for any signs of damage or malfunction. Replace the TCM if necessary.
  5. Refill the transmission fluid to the proper level with the manufacturer-recommended fluid type.

Cost to Fix P1843

The typical repair costs for addressing a P1843 code can vary depending on the specific cause of the issue. In general, the cost of parts such as a new shift solenoid or transmission control module can range from $100 to $500, while labor costs can add an additional $100 to $300. Overall, the total repair cost for this issue may range from $200 to $800. It is important to note that the actual costs can vary based on factors such as the vehicle make and model, the location of the repair shop, and the extent of the repairs needed. It is advisable to obtain quotes from multiple auto repair shops to get a more accurate estimate for the repair.

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Code P1843 Information for Specific Makes

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

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