Sensor Checks
WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
- Inspect the Heated Oxygen Sensors (HO2S) 1 and HO2S 2 for a condition that can affect sensor activity and response. See DIAGNOSTIC AIDS for the following DTCs under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 1.8L VIBE article:
- Inspect the Throttle Position (TP) sensor. A sticking throttle shaft or a binding throttle linkage will causes a high TP sensor voltage. Under these conditions the Powertrain Control Module (PCM) may not control the idle. Monitor TP sensor angle with the scan tool. The indicated angle should be approximately 11 percent with throttle closed.
- Inspect the Engine Coolant Temperature (ECT) sensor. A fixed or inaccurate ECT sensor reading can cause the engine idle to surge or race. Using the scan tool, compare ECT with the ambient air temperature on a cold engine. If the engine coolant is 9°F (5°C) more than or 9°F (5°C) less than the ambient air temperature, check resistance of the coolant sensor. See TEMPERATURE VS. RESISTANCE table. If ECT is significantly less than the ambient air temperature, inspect coolant sensor electrical circuit for high resistance.
- Inspect Mass Air Flow (MAF) sensor operation. Run engine to normal operating temperature. Turn OFF all accessories and observe MAF sensor at idle using scan tool. If MAF sensor reading is more than 3.5 g/s, see DTC P0101: MAF SENSOR PERFORMANCE under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 1.8L VIBE article. If MAF sensor reading is less than 1.0 g/s, check for a vacuum leak between MAF sensor and engine.