1999 Ranger IAC and PCM problems

https://www.justanswer.com/ford/m539u-blowing-pcm-fuse-1997-ford-ranger-2wd-3-0-soon.html

On the intake manifold,

Cleaning your IAC to fix rough idle on 2000 or 2001 Mazda MPV

1999 Ford ranger IAC valve repair

Mazda B2300 Idle Air Control Valves

How to clean the IAC valve Ford Ranger Forum

Hi Michael:
P1504 - Idle Air Control (IAC) Circuit Malfunction
This DTC is set when the PCM detects an electrical load failure on the IAC output circuit.

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

The IAC solenoid resistance is from 6 to 13 ohms.

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watch these videos and you will see what you need to do. 1999 Ford Ranger Idle Air Control Replacement 1999 Ford Ranger cleaning the throttle body part 1 YouTube Testing and Replacing Throttle Position Sensor Ford Explorer you will notice a world of difference.

DTC Description Possible Causes Diagnostic Aides P1504 - Idle Air Control (IAC) Circuit Malfunction This DTC is set when the PCM detects an electrical load failure on the IAC output circuit.

• IAC circuit open
• VPWR to IAC solenoid open
• IAC circuit short to PWR
• IAC circuit short to GND
• Damaged IAC valve
• Damaged PCM

• 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.

P1507 - Idle Air Control (IAC) Underspeed Error This DTC is set when the PCM detects engine idle speed that is less than the desired rpm.

• IAC circuit open
• IAC circuit short to PWR
• VPWR to IAC solenoid open
• Air inlet is plugged
• Damaged IAC solenoid
• Damaged PCM

• The IAC solenoid resistance is from 6 to 13 ohms
• Disconnect IAC valve and look for no change in engine rpm as an indication of a stuck or damaged valve

P1131 - Lack of HO2S-11 Switch, Sensor Indicates Lean A HEGO sensor indicating lean at the end of a test is trying to correct for an over-rich condition. The test fails when the fuel control system no longer detects switching for a calibrated amount of time.

• Electrical:
  • Short to VPWR in harness or HO2S
  • Water in harness connector
  • Open/Shorted HO2S circuit
  • Corrosion or poor mating terminals and wiring
  • Damaged HO2S
  • Damaged PCM
• Fuel System:
  • Excessive fuel pressure
  • Leaking/contaminated fuel injectors
  • Leaking fuel pressure regulator
  • Low fuel pressure or running out of fuel
  • Vapor recovery system
• Induction System:
  • Air leaks after the MAF
  • Vacuum Leaks
  • PCV system
  • Improperly seated engine oil dipstick
• EGR System:
  • Leaking gasket
  • Stuck EGR valve
  • Leaking diaphragm or EVR
• Base Engine:
  • Oil overfill
  • Cam timing
  • Cylinder compression
  • Exhaust leaks before or near the HO2S(s)

A fuel control HO2S PID switching across 0.45 volt from 0.2 to 0.9 volt indicates a normal switching HO2S.

DTC P1506 is set when the PCM detects the engine idle speed is greater than the desired rpm. This is most commonly caused by a dirty or bad IAC valve. Cleaning the throttle body will, most likely, cure this problem.

p1131 means that the bank #1 O2 sensor, the bank closest to the firewall, cylinders 1-3 is showing a lean mixture. Could be a vacuum leak, a misfire on that bank, an exaust leak upstream of the O2 sensor, fuel control or injector problem on that bank, a faulty O2 sensor, faulty PCM, faulty wiring in the engine control wiring harness.

P0171In the vast majority of cases, simply cleaning the MAF sensor does the trick. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling also Inspect all vacuum and PCV hoses, replace if necessaryCheck for a dirty fuel filter and proper fuel pressure

High idle
Changed IAC still the same, shown on scanner IAC 50-60 %, if it set to 40% the Idle is ok. What cause the PCM to set IAC too high? Is any one know?

In my 1996 ranger xl my high idle problem was due to a bad ect sensor. After I replaced that I have had no problems with high idle. Not sure if yours is idleing high all the time like mine was but that sensor fixed the problem for me. Hope this helps!

The torque specs and tightening sequence can be found in Haynes repair manual #36071.Ford Ranger 1993-2005