hey all working on my 96 f 150 4.9 got a couple codes i looked up on trouble codes.net po420 and p1506 i have tried to adress the 1506 with a new iac valve but no fix, the 420 code comes and goes. any help is appreciated. THANKS

 

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The P1506 can be caused by many things, the PCM sets this code when it cannot control engine idle speed within certain limits of IAC valve operation. You need to check for sludge in the throttle body, vacuum leaks, damaged PCV system, or evidence of tampering with the throttle body hard stop.

The P0420 code is likely due to an aging, ineffective catalyst, which will probably require replacement.

Jay

 

On the P1506 code, check your vacuum lines, particularly the vapor line running from the canister purge solenoid to the intake manifold. If this one fails, it will not set an evaporative emissions code. It is a fairly large line, and can suck enough air to prevent the IAC from effectively controlling idle speed. This additional air can also set a false P0420 code because it is un-metered by the MAF, and as a result, at idle, there may be excessive oxygen in the exhaust stream. It could also be a worn out cat, but an o2 sensor simulator will fix that code. Go after P1506 first, and see if P0420 takes care of itself.

 

thanks guys i appreciate it!!!