High Idle at Startup with P0102 and P0134 Codes - 2000 Chevy 3500HD 7.4L Help Needed
Hello, I'm experiencing a high idle issue when starting my 2000 Chevrolet 3500HD 7.4L diesel truck. The problem manifests as a steady RPM of 3200 at startup, and the check engine light is on with two fault codes: P0102 (Mass Air Flow Sensor - Low Voltage Circuit) and P0134 (Oxygen Sensor Circuit No Activity - Bank 1, Sensor 1). I've already replaced the Mass Air Flow (MAF) sensor, Cam Position Sensor, Idle Air Control Valve, and Throttle Position Sensor. Despite these replacements, the issue persists. My question: Could the crankshaft position sensor be the root cause? The P0134 code is particularly confusing — it's not a cam sensor fault but an oxygen sensor circuit failure with no activity detected. Since this code was triggered by the P0102, I'm wondering if there's another underlying issue affecting both sensors. Any insights or suggestions would be greatly appreciated. Thanks in advance!
The P0134 code you're seeing is not related to the camshaft position sensor — it's actually an oxygen (O2) sensor circuit fault with no activity detected on Bank 1, Sensor 1. This code can be triggered by or correlated with the P0102 (MAF low voltage circuit). You mentioned replacing both the MAF and camshaft sensor, as well as the idle air control valve and throttle position sensor. However, since the O2 sensor has no signal, it's important to diagnose whether there's a wiring issue, ground fault, or sensor failure in the oxygen sensor circuit. The absence of activity suggests a possible open circuit, poor grounding, or faulty wiring harness — all of which could be contributing factors. Focus on inspecting the O2 sensor wiring and connections before considering the crankshaft position sensor as a likely cause.