P1632 – Theft Deterrent Start Disable Signal Received (GM)

By Reinier (Contact Me)
Last Updated 2020-08-20
Automobile Repair Shop Owner

Manufacturer Specific Definitions for P1632

Table of Contents

1. What Does Code P1632 Mean?
2. Where is the P1632 sensor located?
3. What are the common causes of code P1632?
4. What are the symptoms of code P1632?
5. Get Help with P1632

What Does Code P1632 Mean?

OBD II fault code P1632 is a manufacturer-specific trouble code that is defined by carmaker General Motors as “Theft Deterrent Start Disable Signal Received”, and is set when the PCM (Powertrain Control Module) detects that an unauthorized ignition key or an ignition key that had lost its programming had been used in an attempt to gain entry into the vehicle. Note that GM anti-theft systems interpret keys with damaged or corrupted programming as unauthorized keys.

For anti-theft systems on GM vehicles to work, several control modules, including the PCM, PIM (Powertrain Interface Module), and the BCM (Body Control Module) are programmed with security codes that are unique to the vehicle they are fitted to. In a fully functional system, these modules communicate with each other every time the vehicle is unlocked or the ignition is turned to the “ON” position to verify and authenticate the security codes that are programmed into each module before the vehicle will start.

However, in practice, the authentication process is a little more complicated, and it follows a precise sequence of events, with each step in the process requiring specific authentications and verifications to complete successfully. These steps are described below-

1) When a door is unlocked or the ignition is turned to the “ON” position, the key in use and the BCM exchange encrypted information to verify that the correct key is used.

2) If the encrypted information transmitted by the key is accepted by the system and the ignition is turned “ON”, the PIM and BCM exchange encrypted information to verify that the security codes in each module match.

3) If the information from the key, BCM, and PIM match, the PIM will confirm this to the PCM via an encrypted message, which will then activate the starting circuit(s) to allow the vehicle to start.

There are many reasons why encoded ignition keys may be seen as unauthorized by an anti-theft system, but regardless of the cause, the PCM will not allow the vehicle to start when such a key is used. When this happens, the PCM will log the event as “Theft Deterrent Start Disable Signal Received”, disable the starting circuits(s), set code P1632, and illuminate a warning light.

Where is the P1632 sensor located?

This image shows a typical GM ignition key that has been disassembled for clarity. The part circled in red is a part of the transponder that communicates with various control modules and security devices on the vehicle to prevent unauthorized entry or use of the vehicle.

What are the common causes of code P1632?

Typical causes of code P1632 are much the same across all GM applications, and could include one or more of the following-

• Damaged ignition key
• In cases where the key is battery-powered, a discharged battery in the key may cause this code to be set
• Failed or failing control modules, including the PCM, PIM, BCM, and others, but note that unlike other codes, failed or failing control modules is a common cause of this code
• Use of an incorrect, unsuitable, or incorrectly programmed PCM, BCM, or PIM, but note that if one or more control modules are to be replaced or reprogrammed, the correct security codes can only be obtained from official GM sources
• Damaged, burnt, shorted, disconnected, or corroded wiring, connectors, and or fuses/fusible links anywhere in the anti-theft system
• Corrupted software/programming in the key and/or in one or more control modules
• Damaged ignition lock
• Low system voltages as the result of a discharged and/or damaged battery

What are the symptoms of code P1632?

Common symptoms of code P1632 could include one or more of the following-

• Stored trouble code and illuminated security warning light
• Multiple additional codes may or may not be present
• It may be impossible to unlock doors, and repeated attempts may trigger audible alarms and/or activate flashing head and indicator lights
• Starting circuits will be disabled, making it impossible to crank or start the engine
• On some GM applications, the engine may start and run for about two seconds or so before shutting off automatically

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