C1241

C1241 is low voltage to the ABS module — the EBCM is seeing supply voltage below its operating threshold (typically under 10V key-on for most platforms, under 9V during cranking) and disabling ABS until voltage recovers. Cheapest first by a wide margin: load-test the battery before doing anything else. A battery that reads 12.4V at rest but drops below 10V under a 200-amp load is the cause of C1241 on probably 70% of cases; replacement is $120-$220 and the code never returns. If the battery passes load test, measure key-on voltage at the EBCM main power connector — it should be within 0.3V of battery voltage; anything more is a wiring/connector resistance problem (commonly a corroded eyelet at the main underhood junction or a chafed positive cable). Check alternator output: 13.8-14.8V at 2,000 rpm with a moderate load (headlights, blower on high). Watch live data for system voltage on the scan tool — should track within 0.2V of what you measure at the battery. The classic expensive misdiagnosis: replacing the alternator ($300-$600) when a $150 battery would have fixed it, because techs assume a charging-system fault without doing the 5-minute battery load test first. Same with replacing the EBCM ($800+) when the actual fault was a corroded battery terminal.

Vehicle-specific patterns: 2004-2012 GM full-size trucks/SUVs — C1241 sets within 2 weeks of a weak/dying battery; AC Delco group 78 replacement fixes it. 2005-2010 Ford F-150 — corroded positive battery cable at the megafuse, replace cable assembly ($85). 2007-2013 Jeep Wrangler JK — undersized factory battery struggles in cold weather, upgrade to group 65 deep-cycle. 2010-2015 Chevy Equinox — C1241 after any jump-start event; battery often damaged by the jump and needs replacement. Estimated repair: $20 to $900.