P1702

What the Code Means

Code P1702 indicates that the transmission control unit (TCU) has detected a fault that puts the transmission into limp-home mode. In this mode performance is limited, often using only one gear, to prevent further damage. The fault can be caused by internal TCU faults, sensor failure, or bus communication issues.

How the Affected System Works

The TCU controls gear shifting, torque converter lockup, and hydraulic system pressure. When it detects a critical fault, the TCU enters a protective mode, reducing load on the mechanical components.

Symptoms

• Engine & Drivability:
• Reduced power
• Inability to shift
• Transmission:
• Transmission stuck in gear
• Indicators:
• Warning lights come on

Diagnosis and Repair

Step 1: Scan

• Use ISTA to read the detailed fault codes.

Step 2: Check the Fluid

• Check the transmission fluid level and condition.

Step 3: Inspect the Wiring

• Check the wiring harnesses and connectors running to the TCU for damage or corrosion.

Step 4: Replace the TCU

• If an internal TCU fault is confirmed, replace the unit (original part number 24001442383).

Step 5: Adaptation

• After the repair, reset the transmission adaptations.

Indirect Issues

Ignoring the fault and continuing to drive in limp mode can lead to:

• Transmission overheating
• Mechanical damage to the clutches and torque converter
• Costly rebuild or transmission replacement