DTC advice - JKowners.com : Jeep Wrangler JK Forum
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post #1 of 2 Old 01-30-2012, 06:51 AM Thread Starter
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Location: Jacksonville, FL
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DTC advice

Past couple of days I've started getting the CEL and Lightining Bolt of doom. using my Aeroforce I've been able to pull the following codes. Sometimes it's just one or two other times it's all three.

P0420 P0441 P0507

P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
Leaded fuel was used where unleaded was called for.
An oxygen sensor is not reading (functioning) properly.
The engine coolant temperature sensor is not working properly.
Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe Retarded spark timing.
The oxygen sensors in front and behind the converter are reporting too similar of readings.

Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
Inspect the downstream heated oxygen sensor (HO2), replace if necessary.
Replace the catalytic converter.

P0441 - Evaporative Emission Control System Incorrect Purge Flow
Bad vacuum switch.
Broken or damaged EVAP line or canister.
Open in PCM purge command circuit.
Open or short in Voltage feed circuit to Purge Solenoid.
Faulty purge solenoid.
Restriction in EVAP solenoid, line or canister.
Corrosion or resistance in purge connector.
Bad PCM.

Common Chrysler fix - Replace Leak Detection Pump / LDP.
Repair damaged EVAP lines or canister.
Repair open or short in voltage feed circuit to Purge Solenoid.
Repair open in PCM purge command circuit.
Replace purge Solenoid.
Replace vacuum switch.
Repair restriction in Evap line or canister or soleniod.
Repair resistance in purge connector.
Replace PCM.

P0507 - Idle Air Control System RPM Higher Than Expected
A vacuum leak
Leaking air intake after the throttle body.
EGR valve leaking vacuum.
A faulty positive crankcase ventilation (PCV) valve.
Damaged/failed/dirty throttle body.
Failed EVAP system.
Failed IAC (idle air controller) or faulty IAC circuit.

This DTC is more of an informational code, so if there are any other codes set, diagnose them first. If there are no other codes, inspect the intake air system for air or vacuum leaks and damage. If there are no symptoms other than the DTC itself, just clear the code and see whether it returns.

If you have an advanced scan tool that can interact with the car, command the idle higher and lower to see if the engine responds appropriately. Also check the PCV valve to see if it's blocked and needs to be replaced. Check the IAC (idle air controller) if equipped, verify it's operation. If available, try swapping in a new throttle body to see if that fixes the problem.

Anyone have any advice on what I should start looking at first? It seems to me that all three could be caused by the Cat going bad... or I could really be screwed and have multiple issues... Don't really want to replace the Cats unless I have to, not on the cheap side, but I dont want to throw money away replacing sensors, etc. either.

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post #2 of 2 Old 01-30-2012, 07:39 AM
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Sounds all like fuel/emission related I'd get a fuel system cleaned an run new tank gas mabe

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