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2003 GMC Sierra 2500 Duramax: P0089, P0380, P0404, P0802, P1093, U2106 - Battery Not Charging Issue Explained

Model: 2003 Sierra 2500 Fault Code: P0089 Posted: 2016-05-11 21:13

Hello, I'm new to this forum and am seeking help diagnosing an issue on my 2003 GMC Sierra 2500 Duramax with Allison transmission. The instrument panel displays the message 'battery not charging' — no specific warning lights or visible symptoms, and the truck starts and runs normally. I used an OBDLink SX scanner to retrieve diagnostic trouble codes (DTCs), which include: - P0089: Powertrain - Fuel Pressure Regulator 1 Performance - P0380: Glow Plug/Heater Circuit "A" - P0404: Exhaust Gas Recirculation Control Circuit Range/Performance - P0802: Transmission Control System MIL Request Circuit/Open - P1093: Manufacturer Defined (Fuel Rail Pressure Excessive or Too Much Differentiation) - U2106: Manufacturer Defined (CAN Message Not Received from TCM) Additionally, P0380 and P0404 are pending. None of these codes directly relate to the 'battery not charging' message. I'm confused — why would the vehicle display this warning with unrelated DTCs? The issue occurred during late evening hours, so I haven't performed further testing. Any insights into whether these codes could be contributing factors or if the battery warning might stem from a different root cause would be greatly appreciated. Thanks, Earl

Related fault codes
P0089P0380P0404P0802P1093U2106
Comments (4)
Anonymous 2016-05-12 07:33

First, I'd like to confirm — is this vehicle stock (no aftermarket chips, modifications, or add-ons)? Just as GM originally built it? FYI: P1093 typically indicates excessive fuel rail pressure or abnormal pressure differentials. U2106 suggests a CAN bus communication failure between the TCM and other modules.

Anonymous 2016-05-12 20:15

I replaced the alternator today after it failed testing at a parts store. Since then, the 'battery not charging' message has disappeared. I haven't re-scanned yet, but I plan to do so in the coming week — even though none of these codes appear directly related to battery charging. I purchased this Sierra several years ago and have no known modifications beyond replacing the muffler with a straight pipe. Thanks for the code explanations. Any additional thoughts on potential root causes would be helpful.

Anonymous 2016-05-13 07:25

Great to hear you resolved it! The fact that there was no voltmeter reading indicating low battery voltage is quite interesting. I’d recommend clearing all stored codes and monitoring the system over the next week. Low voltage can cause multiple sensors to malfunction or report incorrectly, even if the alternator appears functional.

Anonymous 2016-05-13 07:41

Thanks for the advice — I'll clear the codes and monitor the truck over the coming week. Will update if any new symptoms appear!