P2138 — Throttle/Pedal Pos Sensor/Switch D / E Voltage Correlation

P2138 — Throttle/Pedal Pos Sensor/Switch D / E Voltage Correlation. A fault in the throttle and intake air metering. Short, gentle driving to a shop is usually possible. Typical causes: contaminated or failed MAF/MAP sensor, intake air leaks after the MAF sensor, faulty throttle position sensor or pedal sensor.

powertrain (engine/transmission)

Is it safe to drive?

Drive with caution Drive with caution. Many throttle faults put the car into limp mode with limited power — enough to reach a shop, not for highway trips. If the engine stalls or the pedal stops responding, do not drive.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P2138 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the throttle and intake air metering for damage, corrosion, chafing or poor contact.
Subsystem check Inspect and clean the throttle body; check that the plate moves freely.
Subsystem check Watch throttle position and MAF/MAP readings in live data while pressing the pedal — values should change smoothly.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P2138 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P2138 (parts and labor, USD, independent shop rates): Replace the throttle body assembly: $250–$700; Clean the throttle body: $80–$200; Replace the MAF or MAP sensor: $150–$400. Overall, fixing P2138 usually costs between $80 and $700. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What is the most common cause of P2138?

The most common causes are: contaminated or failed MAF/MAP sensor, intake air leaks after the MAF sensor, faulty throttle position sensor or pedal sensor.

What does OBD2 code P2138 mean?

What are the symptoms of P2138?

Drivers most often notice: stalling when coming to a stop, Check Engine Light on, limp-home mode with reduced power, poor throttle response.

How do I diagnose P2138 myself?

Start with a scan: confirm P2138, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the throttle and intake air metering, and verify the suspect component against live data before buying parts.

Is it safe to drive with P2138?

Drive with caution. Many throttle faults put the car into limp mode with limited power — enough to reach a shop, not for highway trips. If the engine stalls or the pedal stops responding, do not drive.

What does P2138 mean?

When P2138 appears on a scan, it means the control module has flagged a problem in the throttle and intake air metering: throttle/pedal pos sensor/switch d / e voltage correlation. The fault sits in the powertrain (engine/transmission) group of the OBD2 standard.

To set P2138, the control module compares live readings of the throttle and intake air metering against calibrated limits, usually over several drive cycles. Alongside the code it stores a freeze frame — a snapshot of rpm, load, coolant temperature and vehicle speed at the moment of failure. Reading that snapshot first saves diagnostic time.

Common symptoms of P2138

stalling when coming to a stop
Check Engine Light on
limp-home mode with reduced power
poor throttle response
unstable or high idle

What causes P2138?

contaminated or failed MAF/MAP sensor
dirty throttle body or stuck throttle plate
intake air leaks after the MAF sensor
faulty throttle position sensor or pedal sensor
failed electronic throttle motor
wiring or connector faults in the throttle circuit

How to diagnose P2138

Connect an OBD2 scanner, confirm P2138 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Visually inspect the wiring harness and connectors related to the throttle and intake air metering for damage, corrosion, chafing or poor contact.
Inspect and clean the throttle body; check that the plate moves freely.
Watch throttle position and MAF/MAP readings in live data while pressing the pedal — values should change smoothly.
Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P2138 does not return.

How to fix P2138

Start with the cheapest and most common causes before replacing expensive parts:

Replace the throttle body assembly — $250–$700
Clean the throttle body — $80–$200
Replace the MAF or MAP sensor — $150–$400

How much does it cost to fix P2138?

Repair cost depends on which component actually failed. Typical scenarios for P2138 (parts and labor, USD, independent shop rates):

Replace the throttle body assembly: $250–$700
Clean the throttle body: $80–$200
Replace the MAF or MAP sensor: $150–$400

Overall, fixing P2138 usually costs between $80 and $700. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.