P2837 Shift Fork “B” Position Circuit Range/Performance

P2837 Possible Causes

  • Outdated Transmission Control Module (TCM) software (reprogram TCM)
  • Faulty Transmission Control Module (TCM)
  • Defective transmission assembly

How to Fix P2837 Code

Check the “Possible Causes” listed above. Visually inspect the wiring harness and related connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Check engine light illuminated (or service engine soon warning light)

P2837 Meaning

There are two electric motors used for shifting gears in the transmission, one for gears 1-3-5 and one for gears R-2-4-6. The gear shift is performed by two shift drums connected to the shift motor pinion via two ideal gears. The maximum shifting force is 1500 N (337 lb). The motors are integrated into the Transmission Control Module (TCM) and operate independently of each other.

P2846 Shift Fork “B” Position Sensor Incorrect Neutral Position Indicated

P2846 Possible Causes

  • Outdated Transmission Control Module (TCM) program (reprogram TCM)
  • Faulty Transmission Control Module (TCM)
  • Defective transmission assembly

How to Fix P2846 Code

Check the “Possible Causes” listed above. Visually inspect the wiring harness and related connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Check engine light illuminated (or service engine soon warning light)

P2846 Meaning

There are two electric motors used for shifting gears in the transmission, one for gears 1-3-5 and one for gears R-2-4-6. The gear shift is performed by two shift drums connected to the shift motor pinion via two ideal gears. The maximum shifting force is 1500 N (337 lb). The motors are integrated into the Transmission Control Module (TCM) and operate independently of each other.

P2836 Shift Fork “B” Position Circuit

P2836 Possible Causes

  • Outdated Transmission Control Module (TCM) program (reprogram TCM)
  • Faulty Transmission Control Module (TCM)
  • Defective transmission assembly

How to Fix Code P2836

Check the “Possible Causes” listed above. Visually inspect the wiring harness and related connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Check Engine Light on (or Service Engine Soon warning light)

P2836 Meaning

There are two electric motors used to change gears in the transmission, one for gears 1-3-5 and one for gears R-2-4-6. The gear shift is performed by two shift drums connected to the shift motor pinion via two ideal gears. The maximum shifting force is 1500 N (337 lb). The motors are integrated into the Transmission Control Module (TCM) and operate independently of each other.

P2853 – ‘A’ Clutch Pressure Discharge Performance

P2853 Possible Causes

  • Low Brake Solenoid Valve
  • Control Valve Assembly

How to Fix Code P2853

Check the “Possible Causes” listed above. Visually inspect the wiring harness and associated connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Check Engine Light illuminated (or Service Engine Soon warning light)

P2853 Meaning

The clutch pressure control solenoid is controlled by signals from switches and sensors. Thus, the clutch pressure is adjusted to be appropriate for the engine load condition and the vehicle driving condition. It becomes possible to finely control the clutch hydraulic pressure with high precision, and a smoother shifting characteristic is achieved.

P2854 – Clutch ‘B’ Pressure Discharge Performance

P2854 Possible Causes

  • High clutch and rear brake solenoid valve
  • Control valve assembly

How to Fix Code P2854

Check the “possible causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Engine light on (or service engine soon warning light)

P2854 Meaning

The clutch pressure control solenoid is controlled by signals from switches and sensors. Thus, the clutch pressure is adjusted to be appropriate for the engine load condition and the vehicle driving condition. It becomes possible to finely control the clutch hydraulic pressure with high precision, and a smoother shifting characteristic is achieved.

P2855 – ‘A’ Clutch Pressure Load Performance

P2855 Possible Causes

  • Low brake solenoid valve
  • Control valve assembly

How to Fix Code P2855

Check the “Possible Causes” listed above. Visually inspect the wiring harness and associated connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Check engine light illuminated (or service engine soon warning light)

P2855 Meaning

The clutch pressure control solenoid is controlled by signals from switches and sensors. Thus, the clutch pressure is adjusted to be appropriate for the engine load condition and the vehicle driving condition. It becomes possible to finely control the clutch hydraulic pressure with high precision, and a smoother shifting characteristic is achieved.

P2856 – Pressure Load Performance of Clutch ‘B

P2856 Possible Causes

  • High clutch and rear brake solenoid valve
  • Control valve assembly

How to Fix Code P2856

Check the “Possible Causes” listed above. Visually inspect the wiring harness and related connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Engine light on (or service engine soon warning light)

P2856 Meaning

The clutch pressure control solenoid is controlled by signals from switches and sensors. Thus, the clutch pressure is adjusted to be appropriate for the engine load condition and the vehicle driving condition. It becomes possible to finely control the clutch hydraulic pressure with high precision, achieving a smoother shifting characteristic.

P2857 – ‘A’ Clutch Pressure Clutch Performance

P2857 Possible Causes

  • Low Brake Solenoid Valve
  • Control Valve Assembly

How to Fix Code P2857

Check the “Possible Causes” listed above. Visually inspect the wiring harness and related connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Symptoms

Possible

Check Engine Light On (or Service Engine Soon Warning Light)

P2857 Meaning

The clutch pressure control solenoid is controlled by signals from switches and sensors. Thus, the clutch pressure is adjusted to be appropriate for the engine load condition and the vehicle driving condition. It becomes possible to finely control the clutch hydraulic pressure with high precision, and a smoother shifting characteristic is achieved.

P2858 – ‘B’ Clutch Pressure Clutch Performance

P2858 Possible Causes

  • High clutch and rear brake solenoid valve
  • Control valve assembly

How to Fix Code P2858

Check the “Possible Causes” listed above. Visually inspect the wiring harness and related connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

Engine light on (or service engine soon warning light)

P2858 Meaning

The clutch pressure control solenoid is controlled by signals from switches and sensors. Thus, the clutch pressure is adjusted to be appropriate for the engine load condition and the vehicle’s driving state. It becomes possible to finely control the clutch hydraulic pressure with high precision, achieving a smoother shifting characteristic.

P2859 – Clutch ‘A’ Pressure Disengagement Performance

Code P2859: Clutch Pressure Control Solenoid Circuit Malfunction

Technical Meaning

The clutch pressure solenoid precisely regulates hydraulic pressure based on:

  • Engine load (RPM, torque)

  • Driving conditions (speed, transmission gear)
    P2859 indicates an anomaly in this circuit, compromising hydraulic control precision and shift smoothness.

Probable Causes

Failure Type Affected Components
Electrical failure • Faulty pressure solenoid
• Short circuit/open in wiring harness
• Damaged connectors (oxidized, bent, pushed-out pins)
Mechanical issue • Sticking valve assembly
• Particle contamination (degraded hydraulic fluid)
Control fault • Erroneous signal from sensors (pressure, temperature)
• Control module error (TCM/ECM)

Symptoms

  • ⚠️ Check Engine Light illumination (“Service Engine Soon”)

  • 🔧 Harsh shifting (jerking, prolonged engagement time)

  • 🚗 Abnormal clutch behavior:

    • Clutch stall

    • Gear slippage

    • Power loss during acceleration

  • 🔊 Hydraulic noises (abnormal clicking or humming)

Diagnostic Procedure

  1. Visual Inspection (Priority)

    • Check solenoid connectors: corrosion, deformed pins, damaged insulation.

    • Inspect wiring harness: signs of rubbing, burning, or crushing.

  2. Electrical Tests

    • Measure solenoid resistance (compare to manufacturer specifications).

    • Check supply voltage and ground (multimeter).

    • Check for short circuits/open circuits with ohmmeter.

  3. Advanced Diagnostics

    • Use a scan tool to:

      • Read live data (solenoid command, measured pressure).

      • Check related codes (e.g., P0868 – Low Pressure Signal).

    • Perform solenoid activation test (via “active command” function).

  4. Hydraulic Check

    • Check fluid level/quality (contamination = frequent cause).

    • Measure clutch pressure (specialized gauge if available).

Repair Solutions

Identified Cause Corrective Action
Damaged connector Clean/tighten or replace connector
Faulty wiring harness Repair wiring or replace damaged section
Solenoid resistance out of tolerance Replace control solenoid
Mechanical blockage Disassemble/clean valve assembly or replace
Erroneous signal Diagnose related sensors/actuators (e.g., pressure sensor)

Critical Note: Poorly controlled clutch pressure can damage clutch discs and synchronizers. Do not ignore this code – prompt intervention prevents costly repairs.

Technical Reference: This fault primarily concerns vehicles with:

  • Dual-clutch transmission (DCT)

  • Automated manual transmission (AMT)

  • Some conventional automatic transmissions.
    Always consult manufacturer specifications for resistance values and specific procedures.