U0901 means the powertrain control module has received data from the ion sense module that is out of range, implausible, or corrupted. The ion sense module monitors ionization current during combustion to help detect knock or misfire events. When the PCM cannot trust that data, it sets this code and may suspend related diagnostics or protective strategies.
Internal damage from heat, vibration, or moisture can cause the module to transmit invalid or intermittent data even though it still communicates on the bus.
Corroded, loose, chafed, or backed-out pins in the harness between the ion sense module and the network/PCM can corrupt data or power signals.
Low voltage, poor ground, or a blown fuse can make the module operate erratically and send out-of-range messages.
Excessive resistance, shorted or open CAN/LIN wires, or electromagnetic interference can distort the messages the PCM receives.
An outdated PCM or ion sense module calibration may misinterpret valid data; a reflash or update can resolve the issue without replacing hardware.
This is uncommon; consider it only if all wiring, power, network, and module possibilities have been ruled out and the PCM still cannot process verified-good data.
Short trips are usually possible, but knock and misfire detection may be disabled, so you should have it diagnosed promptly to avoid risking engine damage.
Usually no. This code is most often caused by the ion sense module, its wiring, power supply, or network issues. PCM replacement should be a last resort after everything else is ruled out.
Yes. Low or unstable system voltage can cause modules to send invalid data, so the battery and charging system should be verified during diagnosis.
Not necessarily. It means the PCM cannot trust the ion sense data, so knock detection may be turned off; actual engine knock is a separate concern that requires further inspection.