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Purchased a 2005 Magnum 5.7L. Couple of Questions...

318 Views 5 Replies 4 Participants Last post by  mattygritt
Purchased a 2005 Dodge Magnum for about $2000 a couple of weeks ago. It needs a lot of front suspension components that have gone bad. Ordered a kit, and am planning on doing that this week. Not too bad from what I've seen on YouTube. I am also having a check engine light for codes P0420 (Catalyst System Efficiency Bank 1) and P1521 (Incorrect Engine Oil Type).

P1521 seems pretty straightforward. Oil change using correct weight oil (5w20). Any ideas on common points as to why the P0420 code goes on with these cars? Common points on the exhaust system to look at?

Also I have a spot on the top of the engine that is missing a bolt... Anyone know what this bolt is for? Here is a picture of it. Car appears to be stock; minus some aftermarket headlights that the previous owner wired in (I hate how people wire aftermarket things, they did an awful job). I'm looking into getting the shorty spark plug wires. I'm seeing the 8.2mm wires for sale. Is there a difference between the 8.2 and 10.4 Taylor shorty wires? That's really all I have thought about for minor mods. It's going to be a family car. Don't need any track/performance upgrades really lol.

Thanks all.
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Thank you both for the replies! Okay... good to know that I am not missing something on the top of the engine. I will leave that bolt hole open for now. The P0420 sounds like it can be a lot. I think I do have an exhaust leak coming from the driver's side. I can hear a slight ticking. Sounds like an exhaust leak. I'll look around that area before I go replacing the converter. It looks like the ehxuast manifold gaskets can be a PITA to replace. Hoping it's not them. Thanks for all the solid advice.
P0420 is the engine computer comparing the upper and lower O2 sensors and deciding your catalytic converter isn't doing enough. Could be as simple as somebody punched a hole in it because it was clogged. You can ignore it pretty much unless where you live you have to pass a smog test.
Yeah I do have to pass an emission test (in a few months). I'm going to look around the driver's side exhaust manifold and connector going to the down pipe. I think I hear a slight leak. Could be that's what is throwing the code. Worst comes worst I'll replace the cat. Thanks for the info.
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