What is the case of Buick Excelle failing to start with code P1631?
3 Answers
Fault code P1631 is defined in Chinese as an incorrect anti-theft program in the Engine Control Module (ECM). 1. Causes: The role of the anti-theft control module is to ensure that the car starts only when the dedicated key is present and matches various components. 2. Engine Control Module: Also known as the Engine Control Unit (on some vehicles, the engine control module and transmission control module are integrated into a Powertrain Control Module), it controls the operation of the entire engine. Its primary function is to control the optimal fuel injection amount and ignition timing. Another important role is to monitor components related to emission control.
I've been a veteran technician at an auto repair shop for over a decade, and I've seen many Buick Excelle owners complaining about no-start issues, with trouble code P1631 being a frequent visitor. This code usually indicates a problem with the generator Fr terminal circuit, meaning there's an error in the generator signal input to the ECM, causing the charging system to fail. When the battery can't charge, naturally the car won't start. Last time, a customer brought in an Excelle with identical symptoms. We diagnosed it as a faulty generator regulator and corroded wiring harness causing poor contact. Replacing the parts fixed the issue. Ignoring this fault could easily lead to a roadside breakdown. Once the battery drains completely, you won't even be able to turn on the lights—it's extremely dangerous. Prevention method: During regular maintenance, have your technician test the generator's output current and apply anti-rust spray to wiring harness connections. Without proper tools, don't attempt DIY repairs—it's safer to visit a professional shop.
My 2010 Excelle had this exact issue - sudden failure to start during cold starts, with error code P1631 showing up. After checking online resources, P1631 indicates the generator Fr terminal signal is out of range, and the ECM considers the charging system abnormal. The mechanic said the generator might have unstable output or damaged cables, causing low voltage and startup failure. In my case, the generator coil was burnt out, and replacing it cost 500 yuan to fix. My advice: if you notice starting difficulties, first check if the battery light on the dashboard is on and inspect the 20A generator-related fuse in the main fuse box for any breaks. If that doesn’t solve it, call a tow truck immediately. Also, pay attention to unusual noises during startup as part of regular maintenance.
