P0E9A DC/DC Converter Voltage Sensor C Circuit Intermittent/Erratic

P0E9A completes the sensor C voltage series of a DC/DC converter. It is meant for a signal that jumps, flickers or drops out for brief moments, which the low and high tests miss because they need a fault to persist. No manufacturer documents P0E9A publicly. The GM tables for channels A and B (25OBDG03A) illustrate the gap: their limit checks sample every 12.5 ms and require 320 failures in a window of 400, roughly four seconds, before a code is stored. Under CARB rules inputs need circuit and range tests and, if possible, a check for implausible values; an erratic code covers the cases in between. Corroded pins, a solder joint with a hairline crack or a wire that rubs through under engine movement are the usual causes, so the warning may come and go.

Likely causes

Symptoms

• Warning lamp that appears and disappears
• Short interruptions of start-stop or 12 V support
• Code often stored as history only

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: law.cornell.edu, gsi.ext.gm.com.