P1838 - Internal Mode Switch 'A' Circuit High Voltage

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3   
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Possible causes

  • Faulty Manual Shift Shaft Position Switch Assembly
  • Manual Shift Shaft Position Switch Assembly harness is open or shorted
  • Manual Shift Shaft Position Switch Assembly circuit poor electrical connection

Tech notes

The automatic transmission manual shift shaft position switch assembly connects electrically to the control solenoid valve assembly. Inspect the automatic transmission manual shift shaft position switch, harness, connector, and control solenoid assembly pins for metallic debris. Use a terminal test kit for any test that requires probing the control solenoid assembly harness connector or a component harness connector. The automatic transmission manual shift shaft position switch assembly can be damaged by currents exceeding 2 mA. Test the automatic transmission manual shift shaft position switch assembly for an open condition whenever a short to voltage condition is observed.

Possible symptoms

  • Engine Light ON (or Service Engine Soon Warning Light)

P1838 Description

The automatic transmission manual shift shaft position switch assembly, also called the internal mode switch assembly, is a dual sliding hall-effect switch attached to the control valve body within the transmission. The 9 outputs from the switch indicate which position is selected by the transmission manual shaft. Four outputs (A, B, C, P) are range selection inputs to the transmission control module (TCM). Five outputs (R1, R2, D1, D2, S) are direction selection inputs to the hybrid powertrain control module. The input voltage at the modules is high when the switch is open and low when the switch is closed to ground. The state of each input is displayed on the scan tool as Internal Mode Switch A/B/C/P and Internal Mode Switch Status D1/D2/R1/R2/S. The Internal Mode Switch Range input parameters represented are transmission range signal A, signal B, signal C, and signal P. The Internal Mode Switch Direction input parameters represented as Internal Mode Switch Status signal R1, signal R2, signal D1, signal D2, and signal Start.
OBDII Code P1838 - Internal Mode Switch 'A' Circuit High Voltage - AutoCodes.com

P1838 Information for specific makes

  • P1838 BUICK Internal Mode Switch 'A' Circuit High Voltage
  • P1838 CADILLAC Internal Mode Switch 'A' Circuit High Voltage
  • P1838 CHEVROLET Internal Mode Switch 'A' Circuit High Voltage
  • P1838 FORD Transmission Transfer Case Shift Motor Circuit Failure
  • P1838 GMC Internal Mode Switch 'A' Circuit High Voltage
  • P1838 LINCOLN Transmission Transfer Case Shift Motor Circuit Failure
  • P1838 MERCURY Transmission Transfer Case Shift Motor Circuit Failure

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P1838 Comments

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