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2021 Terrain Remote Start Not Working & Key Fob Range Issues

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Tom H. · rep 0 · May 22, 3:43 AM · 1 replies · solved · Question

Vehicle: 2021 GMC Terrain SLT

My 2021 GMC Terrain SLT is having problems with the remote start and key fob. The remote start has stopped working completely – when I try to use it, the lights flash, but the engine doesn't turn over. Sometimes I also get a 'Service Theft Deterrent System' message on the dash, but it goes away after I start the car with the key.

On top of that, the range of my key fob seems to have significantly decreased. I used to be able to unlock the car from pretty far away, but now I have to be right next to it. I've already replaced the battery in both key fobs, but it didn't help. Could this be related to the security system or a module issue?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:43 AM

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ClearTheCode admin answer:

It sounds like your 2021 GMC Terrain SLT is experiencing issues that point towards the vehicle's security system, keyless entry system, or related modules. The combination of remote start failure, reduced key fob range, and the 'Service Theft Deterrent System' message are all interconnected.

Common Causes:

  1. Faulty Remote Control Door Lock Receiver (RCDLR): This module is responsible for receiving signals from your key fobs. A failing RCDLR can cause reduced range and issues with key fob functions, including remote start.
  2. Theft Deterrent System Malfunction: The 'Service Theft Deterrent System' message indicates a problem within the vehicle's anti-theft system. This could be a sensor, wiring, or a fault in the Body Control Module (BCM) or Immobilizer Control Module.
  3. Key Fob Programming Issues: While you replaced batteries, the fobs themselves could have lost programming or be faulty, though less likely for both to fail simultaneously.
  4. Wiring/Antenna Issues: Damage to the antenna for the keyless entry system or its wiring could severely impact range.
  5. Low Vehicle Battery Voltage: While the car starts, a weak main vehicle battery can sometimes cause erratic electrical behavior, including issues with modules that control remote functions.

Diagnostics & Next Steps:

  1. Check for OBD Codes: Use an advanced scanner (dealership level) to check for 'B' (Body) codes related to the RCDLR, BCM, or theft deterrent system. Standard OBD-II scanners may not show these specific codes.
  2. Inspect Key Fobs: Ensure there's no physical damage to the key fobs themselves, beyond just the battery.
  3. Vehicle Battery Health: Have your vehicle's main 12V battery tested. A weak battery can cause a cascade of electrical problems.

When to See a Shop:

Given the complexity of the theft deterrent and keyless entry systems, and the specific 'Service Theft Deterrent System' message, it's highly recommended to take your Terrain to a GMC dealership. They have the specialized diagnostic tools (like GM's GDS2) to accurately read codes from all relevant modules, perform specific tests on the RCDLR and theft system components, and reprogram key fobs or modules if necessary. Driving with a compromised theft deterrent system could potentially leave your vehicle vulnerable or cause further starting issues down the line.

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