B1325 – Control Module Power Circuit Low/High Voltage (Chevrolet)

By Reinier (Contact Me)
Last Updated 2021-10-04
Automobile Repair Shop Owner

What Does Code B1325 Mean?

SPECIAL NOTES: As with many other trouble codes, Chevrolet-specific trouble code B1325 is listed with different definitions by different resources. In this case, some unofficial sources list code B1325 with the definition “Control Module Power Circuit Low/High Voltage”, while official GM and Chevrolet sources list code B1325 with the definition “Device power #1 (low current #1) circuit malfunction”.

At first reading, the two definitions might appear to be different, if not incompatible, but the differences merely involve differences in terminology used in different automotive markets. We need not delve into the specifics of these differences here, beyond saying that in the context of this particular trouble code, the terms “Control Module” and” Device Power” both refer to an abnormal power supply to a particular control module other than the PCM (Powertrain Control Module).

Therefore, to avoid confusion, this article will use the definition “Device power #1 (low current #1) circuit malfunction” since this definition indicates the nature of the problem, i.e., a low input current. Note, also, that most recent official GM sources list this code with one of two possible suffixes, these suffixes being-

• DTC B1325 (03)  –  Device Power #1 – “Circuit Voltage Below Threshold”
• DTC B1325 (07)  –  Device Power #1 – “Circuit Voltage Above Threshold”

Therefore, for the sake of clarity, the most accurate rendition of this particular GM/Chevrolet-specific trouble code would be DTC B1325 (03) – Device Power #1 – “Circuit Voltage below Threshold”. END OF SPECIAL NOTES.

Based on the above explanation and depending on the source consulted, OBD II fault code B1325 is a Chevrolet-specific trouble code that typically sets when one of four possible control modules detect an abnormally low battery voltage for a predefined period. Note that since the affected modules draw their power feeds directly from the battery, the battery voltage at any given time is critical for their operation.

In terms of specifics, the following control modules monitor the battery voltage directly and continuously through the B+ (positive battery) terminal, but note that a technical description of the operational relationships between them falls outside the scope of this article-

• The body control module (BCM)
• The instrument panel cluster (IPC)
• The radio/infotainment system
• Sensing and diagnostic module (SDM)

As a practical matter, one, or all of the control modules listed above will set trouble code B1325 when one or all of them detects a battery voltage that falls below 9 volts for longer than 5 consecutive seconds.

When this occurs, the control module that first detects the fault condition will prevent the setting of any other trouble codes and disable all its outputs, except for-

• transmissions on the GMLAN serial communications network
• the Run/Crank relay, which is only disabled after a delay of 3 minutes

In practice though, the action of one control module disabling all its outputs sometimes also disables some or all of the outputs of related control modules. For instance, if say, the BCM (Body Control Module) disables all its outputs, everything that depends on that control module to work will stop working, but in addition, some outputs of the radio/infotainment system, the IPC (Instrument Cluster), and/or the SDM (Sensing and Diagnostic) module will or might also be disabled. See the section on “Symptoms” for more details.

Where is the B1325 sensor located?

This image shows an alternator taken from a Chevrolet Aveo application that consistently undercharged the battery, which is the root cause of code B1325 on GM/Chevrolet applications, more often than not.

Therefore, all diagnostic procedures related to codeB1325 must always start with a) an inspection of the charging system, and b) verifying that all components in the charging system work as designed and intended.

What are the common causes of code B1325?

Common causes of code B1325 could include one or more of the following-

• Defects in the charging system that prevent the battery from achieving and/or maintaining a full charge
• Defective battery, or battery terminals that are loose, corroded, or otherwise damaged
• Failed, or failing alternator components such as the bridge rectifier and/or voltage regulator if the alternator has a built-in regulator
• Damaged, burnt, shorted, disconnected, and/or corroded wiring and/or electrical connectors in the charging system
• Poor engine and/or chassis ground connections, or the intermittent loss of ground connectivity
• Poor, sloppy, or incorrect fitment/installation of aftermarket electrical accessories such as unauthorized audio equipment and auxiliary driving lights
• Previous, but poorly executed electrical repairs and/or modifications
• Disconnecting the battery for any reason
• Failed control module(s), but since this is an exceedingly rare event, the fault must be sought elsewhere before any control module is condemned out of hand

What are the symptoms of code B1325?

The symptoms of code B1325 on GM/Chevrolet applications largely depend on which of the implicated control modules detected and stored the code. Nonetheless, the possible symptoms span a bewildering variety that could include some of the following, but note that the list below is neither complete nor exhaustive-

• Stored trouble code(s), but note that warning lights may or may not be present
• The failure of all body control functions
• All instruments in the instrument cluster may be disabled
• It may be impossible to extract any fault codes other than B1325
• A no crank/no start condition will be present 3 minutes after the code was set and stored; this is an important point because the principal diagnostic test for this code involves measuring and verifying the charging voltage with the engine running
• On automatic models, it may be impossible to move the gear selector out of, or into any position

NOTE: AS a general rule, code B1325 and all symptoms will usually resolve when the root cause of the problem is found and corrected. However, from the above, it should be clear that diagnosing and resolving this code on GM/Chevrolet applications can sometimes be extremely challenging, even for professional mechanics. Therefore, we do not recommend that non-professional mechanics attempt any diagnostic and/or repair procedures when code B1325 is present on any Chevrolet application.