P0A15

P0A15 is the circuit-low variant of P0A14: the engine mount control actuator command line is reading low voltage when it should be commanded high, or the actuator feedback signal has dropped below the expected operating window. The diagnostic ladder shifts from the mount itself to the wiring and the control module: scan-tool the commanded actuator duty (should swing from near 0% at idle to 80-100% during engine-start/stop events on Prius Gen 3), then backprobe the actuator command wire with a DMM during a commanded event (should see 12V switched supply or a PWM pulse depending on platform). A flat 0V reading means an open in the harness or a failed driver FET in the ECU. Inspect the connector at the mount for water intrusion (these mounts sit low in the engine bay and the connector orientation traps salt spray on road-salt vehicles); ohm the actuator solenoid as on P0A14 (5-15 ohms is normal). Confirm the ECU ground at the chassis bond point; a poor ground manifests as both circuit-low and circuit-high faults intermittently. The expensive misdiagnosis is replacing the hybrid ECU when the real fault is a chafed harness wire under the intake manifold. DO NOT probe HV orange-wire circuits with a standard multimeter. Always service HV with Class 0 1000V gloves, isolation tester (Megger), and DC-rated lugged probes; the HV interlock loop drops pack contactors at service-plug removal and must never be bypassed.

Vehicle-specific patterns: 2010-2015 Prius Gen 3 throws P0A15 from harness chafe at the rear of the engine where the active mount wire crosses the firewall heat shield; the chafe creates an intermittent short to ground that the ECU logs as circuit-low. 2012-2015 Prius Plug-In shares the harness routing and the failure mode. 2007-2017 Camry Hybrid throws P0A15 from connector corrosion at the active mount junction on Northeast road-salt vehicles. 2011-2017 Highlander Hybrid throws the code from the same connector pattern. 2005-2012 Ford Escape Hybrid eCVT uses a different mount design and rarely throws this exact code, but when it does the root cause is almost always the connector at the mount itself. Estimated repair: $80 (harness repair) to $600 (mount + harness replacement).