Idle Control System Malfunction
Table of contents
P0505 MERCURY Possible Causes
- Intake air restriction
- Vacuum leaks
- Dirty Throttle Body
- Faulty Electronic Throttle Actuator Control (TAC)
- Electronic Throttle Actuator Control harness is open or shorted
- Electronic Throttle Actuator Control circuit poor electrical connection
- Faulty Powertrain Control Module (PCM)
How do I fix code P0505 MERCURY?
Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector’s pins.
Tech Notes
- There is a factory service bulletin for the following Mercury Models:
- 2005-2007 Mercury Grand Marquis
- 2006-2007 Mercury Mountaineer
- Mercury Factory Service Bulletin OBDII Code P0505
Cost of diagnosing the P0505 MERCURY code
The cost of diagnosing the P0505 MERCURY code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle’s make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.
Possible Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Engine hard to start
- Rough or erratic idle speed
P0505 MERCURY Description
The Powertrain Control Module (PCM) controls the engine idle speed to a specified level through the fine adjustment of the air, which is let into the intake manifold, by operating the Electronic Throttle Actuator Control (TAC). The operating of the throttle valve is varied to allow for optimum control of the engine idling speed. The PCM calculates the actual engine speed from the signals of the crankshaft position sensor (POS) and the camshaft position sensor.
The PCM controls the Electronic Throttle Actuator Control so that the engine speed coincides with the target value memorized in the PCM. The target engine speed is the lowest speed at which the engine can operate steadily. The optimum value stored in the PCM is determined by taking into consideration various engine conditions, such as during warming up, deceleration, and engine load (air conditioner, power steering, and cooling fan operation, etc.).
The Diagnostic Trouble Code (DTC) sets when the desired RPM could not be reached or controlled during the key ON engine running (KOER) self-test.