P2104: The engine computer has forced the engine to idle as a fail-safe because of a throttle control fault

Throttle control forced idle

Severity: Inspect soon

This is a fail-safe that holds the engine at or near idle after a throttle fault, so the car may barely move. Mazda describes speed limited to about 20-25 mph, and KBB warns the car can quickly become undrivable. Get it diagnosed promptly and avoid traffic.

It gets more serious if:

Stop: Stop somewhere safe and have the car towed if the engine suddenly loses most of its power, drops to idle or stalls while you are moving. A throttle that won't respond can leave you unable to keep up with traffic, and Nissan's 2026 throttle body recall says a loss of drive power increases the risk of a crash.

Source: how we rate severity

P2104 in short

P2104 means the engine computer has put the engine into a forced-idle fail-safe after detecting a throttle control problem. It's usually stored with another code that names the real fault, such as a stuck throttle. The car may barely accelerate. If it is in that state on the road, pull over safely and have it towed.

P2104 isn't a fault in one part. It records that the computer chose a protective mode: it limits the throttle so the engine just idles, because it can no longer trust throttle control.

It usually appears alongside the code that triggered it. Mazda's 2010 CX-9 bulletin pairs it with P2111, a stuck-open throttle, and notes speed can be limited to about 20-25 mph. Ford's 2005 Escape Hybrid bulletin pairs it with network and hybrid codes after deceleration.

Diagnosis starts with the other stored codes. Fixing their cause, then clearing codes, normally ends the forced idle.

Most likely causes

Cause 1: Throttle body fault that set another code (such as P2111)
Common general cause
Why it ranks here
The forced idle is a reaction to a throttle problem; Mazda's bulletin pairs P2104 with P2111 from the throttle body.
What would change this
Likelier when another throttle code is stored with it.
How to test the electronic throttle body
Cause 2: Throttle or pedal sensor and wiring faults
Common general cause
Why it ranks here
Pedal and throttle sensor signals must agree; when they don't, the computer falls back to limp-in or idle-only.
What would change this
Likelier if pedal or sensor correlation codes are also stored.
Cause 3: Engine computer, other module or software fault
Supported by vehicle data
Why it ranks here
KBB lists the computer and faults reported by other systems; Ford's Escape Hybrid bulletin pairs P2104 with hybrid and network codes.
What would change this
Likelier when network (U) or hybrid codes are stored with it.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

Step 1: Read every stored code from all modules, not just the engine, and note which set first
Low riskTool: OBD-II or full-system scan tool
- IfA throttle body code such as P2111 or P2112 is stored
  It meansDiagnose that code first.
  Points to: Throttle body fault that set another code (such as P2111)
- IfPedal or throttle sensor codes are stored
  It meansCheck sensors and wiring.
  Go to step 2
- IfNetwork or hybrid system codes are stored
  It meansThe trigger may be in another module.
  Points to: Engine computer, other module or software fault
Step 2: Inspect and test pedal and throttle sensor connectors and wiring to the service manual
Best left to a shopTool: Digital multimeter
Warning:Back-probing sensor and computer circuits can damage terminals or the computer; follow the maker's procedure.
- IfA damaged or corroded connection is found
  It meansRepair it and recheck.
  Points to: Throttle or pedal sensor and wiring faults
- IfWiring tests good
  It meansLook at the throttle body.
  Points to: Throttle body fault that set another code (such as P2111)

Symptoms

Engine stays at idle and won't respond to the pedal Gets more serious: stop and have it checked.
Car limited to a low speed Gets more serious: stop and have it checked.
Check engine light with a wrench or throttle warning light
Engine stalls or won't restart Gets more serious: stop and have it checked.

Compare with: Check engine light with loss of power

How to fix

Step 1: Ask a dealer to check your VIN for open recalls, bulletins or extended-coverage programs for the throttle body or pedal; several makers have published repairs for these codes.

Parts and cost context

Electronic throttle body:P2104 alone doesn't justify a throttle body; replace parts only for the fault behind the other stored code. Labour varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Mazda

2010 · CX-9
Supported by vehicle data
Throttle body fault storing P2104 and P2111 that can cap speed around 20-25 mph. Whether the bulletin is still current is not verified.

SB-01-045-10Status unverified
P2104/P2111 with possible fail-safe speed limit (CX-9)
2010cx-9 · issued August 13, 2010 · NHTSA 10034537
Throttle body may not work properly, setting P2104/P2111; in the worst case fail-safe limits speed to about 20-25 mph.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Ford

2005 · Escape
Supported by vehicle data
Lack of power after slowing down with P2104 alongside hybrid and network codes. Whether the bulletin is still current is not verified.

05614Status unverified
Lack of power after deceleration, MIL and wrench lamp, P1A13/U2023/P2104 (Escape Hybrid)
2005escape-hybrid · issued April 1, 2005 · NHTSA 10017896
Lack of power after deceleration with MIL and wrench lamp and P1A13, U2023 and P2104 on vehicles built 2 Aug 2004 to 7 Feb 2005.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

All Electronic throttle and accelerator pedal codes

P2104 questions

Can I drive with P2104?

Not far. The engine is being held near idle, so the car may not keep up with traffic. Get somewhere safe and have it towed or inspected where it is.

Sources and review

p2104 Code - Throttle Actuator Control System - Forced Idle — Kelley Blue Book (KBB Service Advisor)
SB-01-045-10: P2104/P2111 with possible fail-safe speed limit (CX-9) — Mazda North American Operations / NHTSA , August 13, 2010
What You Should Know About Electronic Throttle Control — AA1Car (Larry Carley)
NHTSA recall 26V081: Electronic throttle body gears may break (2024-2025 Nissan Rogue 1.5L VC-Turbo) — Nissan North America / NHTSA , February 12, 2026
NHTSA ODI Preliminary Evaluation PE13-003: Electronic throttle body malfunction (2009-2013 Escape, Fusion, Mariner, Milan) — National Highway Traffic Safety Administration, Office of Defects Investigation , February 28, 2014
05614: Lack of power after deceleration, MIL and wrench lamp, P1A13/U2023/P2104 (Escape Hybrid) — Ford Motor Company / NHTSA , April 1, 2005
p2106 Code - Throttle Actuator Control System - Forced Limited Power — Kelley Blue Book (KBB Service Advisor)

Last reviewed: October 15, 2026
Written by: Saurabh K.
Editorial review: Pending
Technician review: Technician review pending

This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error

Severity: Inspect soon

Most likely causes

Cause 1: Throttle body fault that set another code (such as P2111)

Cause 2: Throttle or pedal sensor and wiring faults

Cause 3: Engine computer, other module or software fault

What to test first

Step 1: Read every stored code from all modules, not just the engine, and note which set first

Step 2: Inspect and test pedal and throttle sensor connectors and wiring to the service manual