Assalamu Alaikum, readers of The Auto Pulse! Today we have a tricky case study on a Toyota Corolla Cross. The owner complained about intermittent warning lights on the dashboard.
The ABS, Traction Control, and VSC lights would turn ON randomly, stay on for a few days, and then disappear. When we scanned the car, we found a specific trouble code: C1406 - Open or Short in Front Speed Sensor LH Circuit.
In this guide, I will show you how we diagnosed this "intermittent" electrical fault and fixed it without replacing a single sensor. Watch the full diagnosis below.
1. Understanding Code C1406
The code C1406 indicates an issue with the Front Left Wheel Speed Sensor circuit. However, we also found a specific "Info Code" attached to it: 513.
This tells us the sensor isn't necessarily dead—it's just losing signal momentarily. This hints at a wiring or connection issue rather than a bad sensor.
2. Analyzing Live Data
We took the car for a test drive with the scanner connected. Surprisingly, all four wheel speed sensors were showing perfect readings. The graph was smooth, and there were no dropouts during our test.
This confirmed the problem was intermittent. It happens randomly, possibly when hitting a bump or turning the steering wheel.
3. Physical Inspection (Sensor & Wiring)
We removed the wheel and inspected the sensor. It was physically intact but a little dirty. We cleaned the sensor head and the mounting hole to ensure there were no metal particles interfering with the magnetic signal.
We also traced the wiring harness from the wheel hub up to the engine bay. There were no cuts or damages visible on the outside.
4. The Real Culprit: A Loose Pin
We disconnected the sensor connector to inspect the terminals. This is where we found the fault. One of the female pins inside the connector had become loose and expanded.
This restored a tight connection. After clearing the codes, we drove the car for several days, and the light never returned. The loose pin was causing a momentary signal loss (0.5 seconds), triggering the ABS light.
Lesson: Before replacing expensive ABS sensors, always check the connector pins for looseness!
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