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Problem with 1999 Ford Ranger SuperCab
I have a 1999 Ford Ranger 2.5L 2WD. The check engine light is on and displaying 5 codes when I scan it.
P1506 (IAC overspeed error), P0135 (O2 bank 1 sensor 1), P1451 (Evap), P0141 (O2 bank 1 sensor 2), and P1409 (EGR Vac). I need to know how to approach fixing it. While the truck is running, I unplug all the sensors and the truck continues to run. No change in idling whatsoever. Am I looking at a defective PCM? Thanks.
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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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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!
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