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Auto Go
Auto Go, ASE Certified Technician
Category: Ford
Satisfied Customers: 849
Experience:  ASE Master certified, ASE certified Undercar Specialist, ASE Advanced Engine Performance certified
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2004 Ford Explorer: the wrench light came on - which according..limp

Customer Question

My husband wash the engine of our 2004 Ford Explorer. About 2 hours later the wrench light came on - which according to the manual it has something to do with the Electronic throttle control and now I guess it is running in default "limp-home" operation?? Sounds serious. What does this mean since there is no other explanation in the manual. HELP!!
Submitted: 6 years ago.
Category: Ford
Expert:  Auto Go replied 6 years ago.
Hello and welcome to Just Answer!

this vehicle uses an electric throttle control system and has no throttle cable or mechanical link between the accelerator pedal and the throttle body on the engine. This is commonly known as "throttle by wire".

When the wrench light comes on, it signifies that there is a problem with the electronic throttle control system. The system consists of accelerator pedal position sensors, or sensor on the throttle pedal (there are more than one as back ups incase one fails), throttle position sensors out on the throttle body itself and there are more than one of these too and a throttle motor that actually opens and closes the throttle plate.

If the system detects a fault in any of the sensors or the motor itself, it will turn on the wrench light and go into "limp mode". In limp mode, depending on what the computer thinks is wrong, it will either limit the throttle to about 35% or it will command idle and won't let the engine accelerate at all.

It does this because when a sensor fails, the system's ability to control the throttle is compromised and as a safety meausre to keep the engine from accelerating when not commanded to do so, the throttle is limited.

this problem is likely due to water intrusion into a sensor or an electrical connector. I never recommend using a water hose to clean an engine as water can infiltrate connectors and sensors and cause problems.

This is not an easily diagnosed problem and if it doesn't go away when the water dries, will have to be taken to a diagnostic shop to be trouble shot and repaired.

thanks and let me know if you have any more questions.