P06A9

The 5-volt sensor reference rail D is electrically connected but its voltage is out of tolerance — drifting, sagging under load, or noisy instead of a stable 5.00 V. Every sensor fed from reference D then reports skewed readings, which can trigger secondary faults. Causes: a partial short or high resistance on the reference-D circuit, an overloaded rail caused by a shorted sensor, or an internal regulator fault in the module.