I have been having a problem with my truck idling high and not wanting to lose rpm's when I am letting off the gas so I checked the IAC valve and it is perfectly clean. I checked my TPS voltage and it is at .97 which is great. So I hooked up my OBD scanner and I am getting code P1504.

In the manual it states this is: Manufacture controlled vehicle speed, idle control and auxiliary imputs.

Anyone know what this means and where I should go from here?

 

Clean/replace your IAC (it could be stuck)
Unless you have a vacuume leak somewhere

 

Spanky99L- There is nothing to clean. It was almost spotless inside.

 

check above
i edited

 

Thanks. I am going to replace the IAC valve and see if that sloves my idle problem. Everything seems to be pointing towards a sticking IAC valve.

 

ok lemmie know if that fixes it

 

KE2 DTC P0505, P1504, P1507 OR STARTS ONLY AT PART THROTTLE: CHECK VPWR VOLTAGE TO IAC VALVE
Note: If EGR DTC P0402 was output during Self Test, diagnose it first before continuing with this Pinpoint Test.

Disconnect IAC valve.
Key on, engine off.
Measure VPWR circuit voltage at the IAC valve harness connector.

Is voltage greater than 10.5 volts?
Yes No
KEY OFF. GO to KE3 . REPAIR open circuit.


KE3 CHECK IAC VALVE RESISTANCE
IAC valve disconnected.
Measure IAC valve resistance.
Is resistance between 6.0 and 13.0 ohms?
Yes No
GO to KE4 . REPLACE IAC valve.


KE4 CHECK IAC VALVE FOR AN INTERNAL SHORT TO IAC CASE
Measure the resistance from either IAC valve pin to IAC valve case.
Is resistance greater than 10,000 ohms?
Yes No
For DTC P1504:

GO to KE7 .

All others:

GO to KE5 . REPLACE IAC valve.

KE5 CHECK AIR INLET FOR PLUGGING
Inspect the entire intake air system for debris, blockage and other damage.
Remove and inspect IAC air tubes (if equipped) for blockage and other damage.
Remove and inspect the air cleaner element for excessive dirt.
Is the intake air system OK?
Yes No
RESTORE inlet air system. GO to KE6 . REPAIR as necessary.

KE6 CHECK FOR INLET AIR LEAKS
Key on, engine running.
With engine running at idle, listen for vacuum leaks.
Inspect the entire intake air system from the mass air flow (MAF) sensor to the intake manifold for leaks such as:
Cracked or punctured intake air tube.
Damaged or loose IAC air tubes.
Loose intake air tube at air cleaner housing or throttle body.
IAC valve or gasket seal.
EGR valve gasket seal.
Vacuum supply connector and hose.
PCV connectors and hose.
Are any leaks detected in the above areas?
Yes No
REPAIR as necessary. KEY OFF. GO to KE7 .

KE7 CHECK IAC CIRCUIT FOR OPEN IN HARNESS
Note: Refer to the PCM connector pin numbers in the beginning of this Pinpoint Test.

IAC valve disconnected.
Disconnect PCM.
Measure resistance of IAC circuit between PCM harness connector pin and IAC valve harness connector.
Is resistance less than 5.0 ohms?
Yes No
GO to KE8 . REPAIR open circuit.

KE8 CHECK IAC CIRCUIT FOR SHORT TO PWR IN HARNESS
Key on, engine off.
Measure voltage on IAC circuit between PCM harness connector pin and battery negative post.
Is voltage less than 1.0 volt?
Yes No
KEY OFF. GO to KE9 . REPAIR short circuit.

KE9 CHECK IAC CIRCUIT FOR SHORT TO GROUND IN HARNESS
Disconnect scan tool from DLC.
Measure resistance between IAC and PWR GND circuits at the PCM harness connector.
Is each resistance greater than 10,000 ohms?
Yes No
For DTC P1504:

REPLACE PCM.

All Others:

GO to KE10 . REPAIR short circuit.

KE10 CHECK IAC SIGNAL FROM PCM
Reconnect PCM and IAC valve.
Note: If stalling occurs place a shim under the hard stop screw to maintain idle conditions).

Key on, engine running.
Access IAC and RPM PIDS.
With engine at normal operating temperature, accessories OFF and at closed throttle, the IAC duty cycle must be between approximately 22 percent and 45 percent.
Slowly increase engine speed to 3000 rpm and return to closed throttle (Note: If closed throttle rpm is significantly higher than normal, ignore this step).
Is the IAC duty cycle within specification at closed throttle and does the duty cycle respond to the change in rpm?
Yes No
For Continuous Memory DTCs P1504 and P1507:

GO to KE30 .

All others:

KEY OFF. INSPECT throttle body for damage. REPAIR as necessary. If OK, REPLACE IAC valve. RESET Keep Alive Random Access Memory (RAM). (REFER to Section 2, Powertrain Control Module (PCM) Reset ). For DTC P1507, REPLACE IAC valve, otherwise REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) ).

KE20 DTC P1506: CHECK FOR VACUUM LEAKS
Key on, engine running.
With the engine at idle, listen for vacuum leaks.
Inspect the entire intake air system from the mass air flow (MAF) sensor to the intake manifold for damage or leaks such as:
Cracked or punctured intake air tube.
Loose or cracked IAC air tubes.
Loose intake air tube at the air cleaner housing or throttle body.
IAC valve or gasket seal.
Intake manifold assembly or gasket seal.
EGR valve gasket seal.
Vacuum supply connectors and hose.
PCV valve, connectors and hose.
Are any leaks detected in the above areas?
Yes No
KEY OFF. REPAIR as necessary. KEY OFF. GO to KE21 .

KE21 CHECK EVAP SYSTEM FOR A STUCK OPEN VALVE
Disconnect hoses at EVAP canister purge valve (or VMV).
Connect a hand vacuum pump at the fuel vapor port to EVAP canister at the EVAP canister purge valve (or VMV).
Apply 53 kPa (16 in-Hg) of vacuum to EVAP canister purge valve (or VMV).




Does the EVAP canister purge valve (or VMV) hold vacuum for 20 seconds?
Yes No
RECONNECT hoses. GO to KE22 . REPLACE EVAP canister purge valve.

KE22 CHECK IAC VALVE FOR PROPER FUNCTION
Key on, engine running.
Bring engine to normal operating temperature.
Transmission in PARK or NEUTRAL.
Disconnect IAC valve.
Does the rpm drop or engine stall?
Yes No
KEY OFF. GO to KE23 . KEY OFF. INSPECT throttle body for damage. REPAIR as necessary. If OK, REPLACE IAC valve. RESET Keep Alive Random Access Memory (RAM). (REFER to Section 2, Powertrain Control Module (PCM) Reset .)

KE23 CHECK IAC CIRCUIT FOR SHORT TO GND IN HARNESS
Note: Refer to the PCM connector pin numbers in the beginning of this Pinpoint Test.

Disconnect scan tool from DLC.
Disconnect PCM.
Measure resistance between IAC circuit at the PCM harness connector and battery negative post.
Is each resistance greater than 10,000 ohms?
Yes No
For fast idle symptom currently present:

REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) ).

All others:

RESTORE vehicle. GO to KE30 . REPAIR short circuit.

KE30 CHECK IAC SYSTEM FOR INTERMITTENT OPEN OR SHORT
Scan tool connected.
Key on, engine running.
Access IAC PID and RPM PIDs.
With engine at normal operating temperature, accessories off and at idle, the IAC duty cycle must be between 20% and 45%.
Observe the PIDs for an indication of a fault while completing the following at idle:
Lightly tap on IAC valve and wiggle harness connector to simulate road shock.
Grasp the vehicle harness closest to the IAC valve. Shake and bend a small section of the harness from the IAC to the dash panel and from the dash panel to the PCM.
Do the IAC or RPM PIDs suddenly change in value indicating a fault?
Yes No
ISOLATE fault and REPAIR as necessary. For idle quality, starting or stalling symptoms currently present:

REPLACE IAC valve.

 

Good info doug! Where did you get that from? Is it one of those shop repair programs that gives you step by step for almost anything on any car on a computer??

 

Gi Gi.

Is that You ???


I hope you figure this out soon Hank
Here's what I found on it

DTC P1504 Vehicle Speed Output Circuit
P1504 Intake Air Control circuit malfunction.

Code
P1504 - Idle Air Control (IAC) Circuit Malfunction

Description -
This DTC is set when the PCM detects an electrical load failure on the IAC output circuit.

Possible Causes -
IAC circuit open
VPWR to IAC solenoid open
IAC circuit short to PWR
IAC circuit short to GND
Damaged IAC valve
Damaged PCM

Diagnostic Aides -
The IAC solenoid resistance is from 6 to 13 ohms.
IAC valve stuck open
Vacuum leaks
Failed EVAP system
Damaged PCM
The IAC solenoid resistance is from 6 to 13 ohms.

 

Its is a flow chart fo troubleshooting steps from the Ford Service DVD

Gi Gi may have helped write it

The first letters are the step number

If you read it carefully you can see that it is a linear if, then process..

 

I think he got it here: http://www.flippedbit.net/F150/obdII_codes.htm

Dan

 

Well I ran into this problem today but my question is after unplugging the IAC while its running it does drop a little in rpm not much but a little does this mean I have a leak somewhere?? Ive checked and cant seem to find one??? or could it still be a bad IAC?? My truck idles higher than normal for about 2 days in a row and bam here comes the error code it stays high in all driving conditions in park in drive all the time...

 

Well I replaced the IAC with a new one and guess what? still idles very high... I dont know my next move but do know its pissing me off...

 

non-stock throttle body? Check the TPS, etc?

 

Didnt think of that..
Thanks Ive been so focused on other things IAC related I'll take a look at that it is an aftermarket SBTB...