Dodge Neon ES 2001 P0340 and P0134 Codes: Causes, Fixes, and Fuel Efficiency Impact
Hi everyone, I own a 2001 Dodge Neon ES with a recurring check engine light issue that's been persisting for about 5-6 months. The warning light turns on intermittently, stays off for several days, then comes back on again — this cycle repeats consistently. The car has been driven approximately 87,000 miles, mostly in Maine, and is now being used in Dallas, Texas. It starts smoothly with one key turn and I’ve never experienced any loss of engine power or performance during driving. Recently, I visited AutoZone where they diagnosed two OBD-II codes: P0340 (Camshaft Position Sensor Circuit Malfunction) and P0134 (Oxygen Sensor 1-1 Circuit Malfunction). I appreciate their free diagnostic service. I’ve long suspected the fuel cap might be causing this erratic behavior, but I’m now wondering if that’s actually relevant to these specific codes. Are there any other possible causes? Should I still take it to a mechanic? I'm concerned about being overcharged or subjected to unreliable repairs. Any real-world experiences or technical insights on how to fix P0340 and P0134 in a 2001 Dodge Neon ES would be greatly appreciated. Thanks for your help! Best regards, Babs Mohan
The fuel cap is not related to P0340 or P0134 codes. These issues are typically caused by a faulty camshaft position sensor and a failing oxygen sensor. On 2001 Dodge Neon ES models, this combination is quite common. Replacing both components will resolve the problem. Without proper camshaft signal timing, fuel injectors won't function correctly, leading to poor fuel efficiency. A malfunctioning O2 sensor can also cause incorrect air-fuel mixture adjustments, increasing fuel consumption. Fixing these parts promptly is recommended to maintain engine performance and fuel economy.