P2105 Code: Throttle Actuator Control System – Forced Engine Shutdown
The engine computer shut the engine off on purpose because it could no longer control the throttle safely.
Stop driving
Do not drive. If the engine dies on the road, shift to neutral, steer firmly to the shoulder and brake hard and steadily – steering gets heavy and brake assist fades after a few pumps. Have the car towed and don't keep cranking it in traffic.
At a glance
Severity: Critical
- Meaning
- Throttle Actuator Control System – Forced Engine Shutdown
- System
- Speed & Idle Control · Powertrain
- Safe to drive?
- No — stop driving
- Typical repair cost
- $150–$1,600
- DIY difficulty
- Hard
P2105 is the last step in the electronic throttle fail-safe ladder. Reduced power (P2106), limited rpm (P2110) and forced idle (P2104) all keep the engine running; P2105 means the PCM concluded that even idling wasn't safe and cut fuel and spark. Typical triggers are a throttle that stays open while the pedal is released, throttle and pedal sensors that disagree so badly the PCM can't tell where the plate is, or its own watchdog processor reporting a fault. Low supply voltage and damaged shared sensor wiring can produce the same picture. The engine may die while driving, or start and stall within a second or two on every attempt. As with the other fail-safe codes, look for the companion code first.
How to read P2105
- P Powertrain
- 2 Generic (SAE)
- 1 Fuel & air metering
- 05 Specific fault
Symptoms
- Engine shuts off while driving without warning
- Engine starts, then dies after one or two seconds every time
- Heavy steering and a hard brake pedal after the engine stops
- Check engine light plus electronic throttle or wrench light
- Throttle-related codes such as P2111, P2135 or P2138 stored alongside
- Idle was racing or the car pushed against the brakes just before shutdown
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Throttle plate stuck open or not returning – broken spring, carbon, ice or damaged gears
- Pedal and throttle position sensors disagreeing at the same time
- Internal PCM monitoring or processor fault
- Low supply voltage or poor PCM grounds during the monitoring check
- Damaged harness affecting shared sensor reference or ground circuits
- Replacement throttle body not relearned or wrong part fitted
Diagnosis step by step
Secure the car and read every code
Leave the car parked safely and read codes from all modules. Note the order and the freeze frame: a stuck-open code (P2111) or a sensor correlation code (P2135, P2138) before P2105 is the lead to follow.
Tools: OBD-II scanner
Check the throttle plate by eye
Ignition off and key well away from the car, remove the intake duct. At rest the plate should sit just slightly open; if it hangs wide open or won't spring back after you gently press it, the throttle body is the problem.
Tools: Flashlight, Gloves
Watch the key-on self-test
With the duct off and hands clear, have a helper switch the ignition on. Most electronic throttles sweep briefly and settle; compare the two throttle position readings and the pedal readings in live data – they must agree without jumps.
Tools: OBD-II scanner
Verify power and grounds to the PCM
Check battery condition, then measure voltage drop on the PCM ground and supply circuits while cranking. Losses of more than a few tenths of a volt can reset or confuse the monitoring processor.
Tools: Multimeter
Test shared sensor circuits
Measure the 5-volt reference and sensor ground at the throttle body and pedal. A reference pulled low or a floating ground affects both sensors at once, which is exactly the kind of contradiction that ends in a forced shutdown.
Tools: Multimeter
Update or replace the PCM only last
If the throttle body, sensors and wiring all check out, ask a dealer about a software update for throttle monitoring. Replacing the PCM requires programming to the vehicle and is the last step, not the first.
Tools: OBD-II scanner
Where the parts are
- 1Battery
- 2Alternator
- 3Engine computer (ECM)
- 4CAN bus
- 5Transmission
- 6Wheel speed sensor
- 7High-voltage battery
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Tow to a shop and diagnose | No | $150–$350 |
| Replace electronic throttle body and relearn | No | $350–$950 |
| Replace accelerator pedal sensor | No | $150–$450 |
| Repair shared sensor wiring or grounds | No | $150–$500 |
| Update, or replace and program, the PCM | No | $150–$1,600 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Emissions / smog test impact
Will fail
An engine that shuts itself down can't be tested, and the stored codes light the check engine light – an OBD emissions test fails. Retest only after the repair and several normal drives.
Frequently asked questions
Why would the computer turn my engine off deliberately?
If the PCM can't confirm that the throttle is where it should be, a running engine could accelerate on its own. Shutting it down is the safest choice it has left, even though losing the engine in traffic is dangerous too.
Do brakes and steering still work when the engine stops?
Yes, but with more effort. Brake assist lasts for one or two firm applications from stored vacuum, so press hard and steadily instead of pumping. Hydraulic power steering gets heavy; electric power steering usually keeps working while the ignition is on.
My engine starts and dies straight away – is that P2105?
It can be. If the PCM finds the throttle fault during start-up it will shut the engine off again immediately. Read the codes before replacing a fuel pump or immobilizer parts, which cause similar symptoms.