123701

What the Code Means

Code 123701 points to a fault in the turbocharger wastegate actuator — the DME can't determine the closed position of the wastegate flap. That means the actuator rod has play or the wrong length, so the flap can't close fully. As a result, the turbocharger can't build the required boost pressure.

The boost control system uses the wastegate actuator to regulate pressure. The actuator is connected to a rod that moves the flap. If the rod length is out of spec (too short or too long), the flap won't close completely, which causes a boost loss.

Symptoms

• Engine: reduced power, limp mode
• Behavior: boost loss, sluggish acceleration
• Indicators: error messages on the instrument cluster, Check Engine

Diagnosis and Repair

Step 1: Read the Codes

Use ISTA or INPA to read the fault codes. Confirm that code 123701 is active.

Step 2: Check Rod Play

Measure the play on the wastegate actuator rod. If play exceeds 0.08 in (2 mm), adjustment is needed.

Step 3: Adjust Rod Length

• Turn the rod's adjustment nut: 1 turn = 0.04 in (1 mm) of length change.
• Bring play down to the minimum (under 0.08 in (2 mm)).

Step 4: Calibration

After adjusting, run a wastegate calibration with dealer software (ISTA).

Step 5: Check the Wiring (B38/B48 Engines)

If adjustment doesn't help, check the actuator wiring harness for electromagnetic interference (EMC).

Step 6: Replace the Turbocharger

If the wastegate flap has mechanical play (worn seat), the turbocharger needs replacement.

Secondary Problems

Ignoring the fault leads to permanent limp mode and reduced power. Running for a long time with the flap in the wrong position can damage the wastegate seat or the turbine housing, which will require turbocharger replacement. A turbocharger replacement is a very expensive repair.