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1999 Dodge Durango 5.2L Engine P0505 Code: Diagnosis and Solutions After Multiple IAC Replacements

Model: 99 Dodge Durango Fault Code: P0505 Posted: 2010-02-25 23:51

I own a 1999 Dodge Durango with a 5.2L V8 engine (171,000 miles) that has been plagued by the P0505 code for over a year. I initially believed this was solely an idle air control (IAC) valve issue and purchased the vehicle with that expectation in mind. After replacing the IAC valve four times—two myself and two at the dealer—I’ve tried every known fix, including cleaning terminals, installing new wiring harnesses, and using a used IAC from the same model year. The car has stalled multiple times, often unexpectedly. Each time it stalls, I can restart it by keeping my foot on the floor and maintaining over 3000 RPM for about 10 minutes. It typically runs fine until the next failure occurs. A peculiar pattern I’ve noticed is that during cold weather, the check engine light occasionally turns off for one to two days but always returns within a few days. I’m now considering replacing the powertrain control module (PCM), though I’m hesitant due to the $150 troubleshooting cost and the fact that my friend’s Durango no longer has a usable PCM. Is there any way to diagnose or test the PCM without purchasing a new one? Could other components—such as the alternator, battery, intake gaskets, or vacuum leaks—be contributing to this issue? Any insights into potential root causes beyond IAC or PCM failure would be greatly appreciated.

Related fault codes

P0505

Comments (3)

Anonymous 2010-02-26 15:46

The P0505 code can sometimes occur when the charging system voltage is too low, causing the powertrain control module (PCM) to lose accurate airflow readings. This may point to a failing alternator or weak battery. Additionally, if someone has previously adjusted the throttle body's set screw in an attempt to fix idle issues, it’s worth testing with a used throttle body. Another possibility: intake gaskets or plenum pan leaks on 5.2L Durangos can create vacuum loss, leading to misfires and oil consumption—this could result in low vacuum readings and trigger the P0505 code. Always verify the accuracy of the manifold absolute pressure (MAP) sensor and throttle position sensor when diagnosing idle-related problems.

Anonymous 2011-05-22 19:10

I had a 2000 Dodge Durango 5.9L with P0505. I replaced both the PCM and IAC valve—still got the same code. When I unplugged the IAC and cleared the system, the error persisted. This confirms that neither the IAC nor the PCM is the root cause. After testing with a portable battery charger during startup, the code disappeared entirely. I’ve since returned both aftermarket PCMs and am keeping only the new IAC. I will never buy another Dodge again. Dodge service is terrible—why do they assign an IAC fault when the real issue is low battery voltage? Why not set a 'low battery' diagnostic code instead? At dealerships, they often say 'we’ve never seen this before,' and then require full replacements to fix it—this is unreasonable and costly.

Anonymous 2011-05-24 04:45

The vehicle does indeed generate a P0505 fault when battery voltage is low. However, the diagnostic criteria for setting that code differs from what the PCM requires to detect actual idle instability. It's fundamental best practice in fuel-injected diagnostics to always inspect the charging system and battery health before addressing any fuel injection or idle-related issues. Your frustration stems from being unable to diagnose the root cause—this isn’t a manufacturer failure, but rather a limitation of relying solely on part replacement without proper diagnostic testing.