C6 Corvette No Fobs Detected: Causes, Diagnosis and Fixes

If your C6 Corvette flashes NO FOBS DETECTED and refuses to crank, or the doors stop opening when you squeeze the handle pad, the problem is usually smaller and cheaper than it looks. Most cases come down to a weak fob battery, a tired car battery or something in the cabin jamming the signal. A smaller number are a failing keyless entry module, which GM has a specific bulletin for. This guide explains how the C6 keyless system works, what makes it lose the fob, how to narrow it down in your driveway and which repair makes sense once you know the cause.

Quick Answer

• Try the glove box pocket first. Put the fob in the small pocket inside the glove box, buttons facing the passenger side, press the brake (or clutch) and press START. If the car starts, the fob and the immobilizer are fine and you are chasing a weak fob battery, interference or the keyless module's antenna circuit.
• Replace the fob battery. The C6 fob uses one CR2032 coin cell, installed positive (+) side down. GM's own check is that the battery should read between 2 and 3 volts.
• Check the car battery. A weak or recently disconnected battery causes a lot of keyless glitches. Charge it fully and test it before you buy any parts.
• Look for interference. Phone chargers, aftermarket radios and their interface modules, dash cams, radar detectors and power inverters are common culprits. GM says swapping the fob or the receiver will not fix an interference problem.
• If none of that works, GM's 2014 bulletin points to a failed transistor inside the keyless entry module (RCDLR). The fix is a replacement module programmed to your car.

Which Corvettes Are Affected?

Every 2005-2013 C6 Corvette has keyless access with push-button start, from base coupes and convertibles to the Grand Sport, Z06 and ZR1. GM's bulletins cover all C6 years, plus the 2004-2009 Cadillac XLR, which shares the system.

The message itself can read NO FOBS DETECTED or NO FOB DETECTED depending on the year and the situation. You may also see related messages such as FOB BATTERY LOW or a prompt asking whether you want OFF or RUN when the car can no longer see a fob after the engine is running.

Symptoms of a C6 No Fobs Detected Problem

• NO FOBS DETECTED on the driver information center (DIC) when you press START, and the engine will not crank
• The car starts every time with the fob in the glove box pocket but not with the fob in your pocket
• Passive entry stops working on one door or both, even though the lock and unlock buttons on the fob still work
• The problem comes and goes with temperature, after a long drive or when the car has sat for a while
• The message showed up right after a battery change, a jump start or a battery disconnect
• The problem started after installing a radio, phone charger, dash cam or other accessory
• FOB BATTERY LOW on the DIC, or fob buttons that only work from very close to the car

How the C6 Keyless System Works

Knowing the parts makes the diagnosis much easier. GM's service information describes four main pieces.

• The key fob. It's a two-way radio. The car sends it a low-frequency challenge, and the fob answers on a radio frequency the car can hear. The fob also carries a fold-out or detachable emergency key blade for the mechanical locks. The C6 can learn up to four fobs.
• The keyless entry module. GM calls it the remote control door lock receiver, or RCDLR. It receives the fob's answer, runs the passive entry and immobilizer logic, and tells the engine computer whether to allow fuel. On the C6 it also handles other jobs. It controls the automatic transmission shift lock, and it's the receiver for the tire pressure sensors, which is why a bad module can cause more than one symptom. It sits high in the dash on the passenger side, above the radio.
• The antennas. The RCDLR drives a backup antenna behind the glove box pocket plus three more low-frequency antennas for passive entry. The glove box antenna is the one used for starting, and the pocket next to it is designed to work even when the fob battery is weak or the signal is being jammed.
• The body control module (BCM). The RCDLR isn't on the same high-speed network as the engine computer, so it talks to the engine computer through the BCM. A BCM or wiring problem can block the "OK to start" message even when the fob is detected.

When you press START with the brake applied, the RCDLR has the glove box area antenna send a challenge. A programmed fob answers, and the RCDLR sends a fuel enable message through the BCM to the engine computer. If no valid answer comes back, you get NO FOB DETECTED and no crank.

What Causes No Fobs Detected on a C6?

1. A Weak or Dead Fob Battery

This is the most common cause by far. The fob has to answer the car every time you open a door or press START, so the battery works harder than in a conventional remote. GM's 2005 owner's manual estimates about three years of battery life. Battery contacts that have spread apart or a battery that was put in upside down cause the same symptoms.

2. A Low or Unstable Car Battery

The RCDLR needs steady voltage to power its antennas. A battery that is weak, partly discharged from sitting or recently disconnected can cause NO FOBS DETECTED, a fob that has to be relearned or other strange behavior. C6 owners often report the message showing up right after a battery replacement or jump start, then going away once the battery is fully charged and the system has been reset.

3. Radio Interference

The keyless system runs on low-power radio signals, so other electronics can drown it out. GM's keyless access bulletin calls out cell phone chargers (even with no phone plugged in), two-way radios, power inverters and computers. It also mentions gas stations with pay-at-the-pump transponders and parking directly under a radio tower. Owners have traced the message to aftermarket head units and their interface modules, satellite radio antennas and radar detectors. Interference usually shows up as an intermittent problem tied to a place, a plug-in device or a recent install.

4. A Failed Keyless Entry Module (RCDLR)

GM's 2014 bulletin describes a C6 that won't crank and may not open through passive entry, but always starts with the fob in the glove box pocket. GM blames a transistor inside the RCDLR that stops driving the antennas properly. Owners also report modules that fail only in cold weather or heat, connector pins that need cleaning and moisture damage inside the module.

5. A Glove Box Antenna or Wiring Problem

If even the glove box pocket won't start the car with a fresh fob battery, look at the backup antenna behind the pocket and its wiring. Owners have found the antenna popped out of its mounting clip, and loose connectors or poor grounds near the passenger-side modules can cause the same no-start.

6. Door Handle Switch Problems (Passive Entry Only)

If the car starts normally but one door won't open when you squeeze the handle pad, the fob probably isn't the issue. Each door has a small electronic switch pad (GM 22751230 on both sides) that tells the system you want in. These pads wear out or get dirty. If the fob's unlock button works but the pad doesn't, suspect the switch.

7. A Fob That Isn't Programmed or Was Lost From Memory

A new or used fob has to be learned to your car before it will work. Fobs can also need relearning after some battery or module work. A fob the car doesn't know will cause NO FOBS DETECTED even though its battery is fine.

What GM Says About No Fob Detected

GM has published three pieces of service information on this.

• Keyless Access System bulletin 08-08-47-001 (March 2008). This covers 2005-2008 Corvettes and the XLR. It explains how passive entry and push-button start are supposed to work and lists common interference sources. It gives a simple interference test (below) and tells dealers not to replace the receiver for interference concerns, because new parts won't fix it.
• Preliminary Information PIC5961 (February 2014). This covers 2005-2013 Corvettes and 2004-2009 XLRs with NO FOB DETECTED and a possible no-crank, where the car always starts with the fob in the pocket. The steps are to charge the car battery, check that the fob battery reads 2-3 volts and then listen to the RCDLR when you press START. A series of clicks is normal. A single click means the module's internal transistor has failed and the RCDLR should be replaced.
• Preliminary Information PIC3225J (2018). This covers setting up a replacement RCDLR on 2005-2013 Corvettes. A new module has to have the fobs programmed, an RCDLR setup run with a scan tool, a theft deterrent relearn with the engine computer and a tire pressure sensor learn.

What This Means for You Today

GM's first step is never "replace the module." The dealer is told to rule out the car battery, the fob battery and interference first. When the module really is the problem, a replacement has to be programmed to your car, so a used RCDLR from another C6 won't simply plug in and work.

How to Diagnose No Fobs Detected on a C6

Work through these steps in order. Most cars are sorted out by Step 3.

Step 1: Charge and Test the Car Battery

Put the battery on a charger or tender until it's fully charged, and have it load tested if it's more than a few years old. If you recently disconnected or replaced the battery, re-index the windows afterward (see our C6 window indexing guide) and try the fob again.

Step 2: Check the Fob Battery

Open the fob and pull the CR2032. A meter should read between 2 and 3 volts. If it's low, or you don't know how old it is, replace it. Put the new battery in positive (+) side down, and make sure the contacts are touching it firmly. Wipe the contacts with a clean, dry cloth while you're in there.

Step 3: Try the Glove Box Pocket

Open the glove box and put the fob in the small pocket with the buttons facing the passenger side. Press the brake (or clutch) and press START.

• It starts in the pocket but not from your pocket: The fob is programmed and the immobilizer is working. Focus on the fob battery, interference and the RCDLR (Step 5).
• It won't start even in the pocket: Try a second fob. If neither works, check the car battery again, then look at the glove box antenna, the wiring and the RCDLR. A fob the car doesn't recognize can also do this.

Step 4: Rule Out Interference

Unplug everything from the power outlets, including phone chargers, and take any loose electronics out of the car. If you have an aftermarket radio, remote start, dash cam or radar detector, disconnect it completely. Owners have found that pulling the fuse isn't always enough. Then use GM's test. Hold the fob right next to a suspect device and press START. If NO FOB DETECTED appears only when the fob is near that device, you've found the cause. Also try the car somewhere else if it only acts up at home, at work or at one gas station.

Step 5: Listen to the Keyless Module

With a known-good fob in the cabin (not in the glove box pocket), have a helper press START while you listen near the top of the dash above the radio. A series of quick clicks is normal. Just one click is the failure GM describes in PIC5961, and the RCDLR needs to be replaced.

Step 6: Test the Door Handle Switches

If only passive entry is the problem, try the fob's unlock button and squeeze each door's handle pad with the fob in your pocket. If the button works but one door's pad never responds, the handle switch on that door is the likely cause. Also keep in mind that if you hold the fob right up against the door, the car may think the fob is inside and ignore the pad. GM says to step back a little and try again.

Step 7: Scan for Codes

A scan tool that can talk to the body modules (a GM Tech 2 or a capable aftermarket tool) can read RCDLR and BCM trouble codes, show whether the module sees each fob and check the communication between the RCDLR, BCM and engine computer. If you've reached this point without an answer, a scan is worth it before you buy a module.

Fix Options Compared

1. New Fob Battery

The cheapest fix and the right place to start. A 5-pack of CR2032 fob batteries covers both fobs with spares. If the fob shell is cracked or the battery contacts are loose, a replacement fob shell lets you move the circuit board into a new case.

2. Charge or Replace the Car Battery

If the car sits for weeks at a time, a Corvette battery tender keeps the voltage up and helps prevent repeat keyless glitches. If the battery is dead and you can't get in, the C6 has a mechanical backup. Use the fob's key blade in the rear lock cylinder, then use the emergency door release in the rear compartment. Some owners also add an emergency access port. It puts a pair of hidden power leads near the grille, so you can hook up a charger or another car's battery to power the door locks and get in. It also works as a tender hookup during storage, but it isn't meant for jump starting.

3. Replacement Key Fob

If one fob works and the other doesn't, the bad fob is the problem. We stock used C6 fobs and new C6 fobs.

The original 2005-2007 fobs (GM 10372541 and 10372542) are no longer made. GM now lists the later-style fob (GM 25926479 and 25926480) for every 2005-2013 Corvette, and it programs and works in a 2005-2007 car, glove box pocket included. The catch is the emergency key blade. The later fob takes a detachable key blank (GM 25995382), which is sold separately and is narrower than the 2005-2007 key:

• 2008-2013: Have the blank cut to match your key.
• 2007: The blank fits the locks and can usually be cut to match your key. It won't work if your key has any uncut, full-width positions (number 1 cuts).
• 2005-2006: The blade won't work in the original rear and glove box lock cylinders unless you replace them. The fob itself still unlocks and starts the car normally. Any replacement fob has to be programmed to the car, and our C6 key fob programming guide walks through it. You can browse everything in our Corvette key fobs category.

4. Glove Box Backup Antenna

If the car won't start even with a good fob in the pocket, check the antenna behind the glove box pocket. Make sure it's clipped in place and plugged in. A used C6 glove box antenna and its mounting bracket fit all 2005-2013 cars.

5. Door Handle Switch

If passive entry fails on just one door, replace that door's handle pad. Both doors use the same switch. Choose a used C6 door handle switch or a new C6 door handle switch.

6. Reprogrammed Keyless Entry Module (RCDLR)

When the single-click test points to the module, or you've ruled out everything else, the RCDLR needs to be replaced. GM's last service numbers were 25940664 for 2005-2007, 25938511 for 2008-2009 and 25971235 for 2010-2013, and all three are discontinued. Each replaced several earlier numbers, so read the label on yours and match it. A used module from another car holds that car's data, so it won't work in yours as-is.

Our C6 reprogrammed used keyless entry module comes programmed to your car. If you'd rather keep your original module, or you already have a matching used one, our keyless module reprogramming service handles the programming. Our C6 keyless entry module guide explains how both options work. For a quick look at why C6 modules are matched to the car, see C6 module replacement basics.

A reprogrammed module is a clone of your original. It carries your car's fob, theft deterrent and tire pressure sensor data, so it plugs in and works with no fob programming, theft relearn or tire pressure learn. That's different from installing a new or uncloned module. GM's procedure for those calls for four steps after install: program the fobs, run Setup New RCDLR with a scan tool, do a theft deterrent relearn with the engine computer and do a tire pressure sensor learn. On cars with a steering column lock, GM also calls for a new column lock module.

If a fob or a tire pressure reading still doesn't show up after install, our fob programming guide and C6 TPMS reset guide cover the relearns you can do yourself.

7. Body Control Module

The BCM is rarely the cause of NO FOBS DETECTED. It can be if a scan shows communication faults between the RCDLR and the engine computer, or if you have other body electrical problems at the same time. Like the keyless module, the C6 BCM is programmed to the car. Our C6 reprogrammed used body control module and C6 BCM reprogramming service cover both routes, and the C6 body control module guide explains the details. Browse all modules in Corvette computers and modules.

Which Fix Should You Choose?

• The car starts in the glove box pocket: Replace the fob battery and remove interference sources first. If the problem continues and the RCDLR gives a single click, replace the module.
• One fob works and the other doesn't: Replace the battery in the bad fob. If that doesn't help, replace the fob and program it.
• Nothing works, even in the pocket: Charge the car battery and try both fobs. Then check the glove box antenna and wiring. Scan before you buy a module.
• Only one door ignores the handle pad: Replace that door handle switch.
• The car also gets stuck in Park, or tire pressures go blank: The RCDLR handles those too, so a module fault is more likely. See C6 Corvette stuck in Park.

Frequently Asked Questions

Can I Still Drive My C6 If It Says No Fobs Detected?

If the car starts with the fob in the glove box pocket, yes. Keep the fob there until you fix the cause. If the message appears while you're driving, the engine keeps running, but the car may not restart after you shut it off unless the fob is detected.

What Battery Does a C6 Corvette Key Fob Use?

One CR2032 coin cell, installed positive (+) side down. It's the same for 2005-2007 and 2008-2013 fobs.

Will a 2008-2013 Fob Work on a 2005-2007 C6?

Yes. The later fob programs and works in any C6, including the glove box pocket. Only the emergency key blade differs. It can usually be cut to fit a 2007, but 2005-2006 cars need new rear and glove box lock cylinders to use it.

Do I Need to Reprogram My Fob After Changing the Battery?

Normally no. A battery change alone shouldn't erase the fob. If the fob still isn't recognized with a fresh battery, try the glove box pocket, then try reprogramming with our key fob programming guide.

Can I Swap in a Used Keyless Entry Module From Another C6?

Not as-is. The RCDLR stores the fob and theft deterrent data for the car it came from. It has to be programmed to your car, either by cloning your original module or by running GM's setup with a scan tool.

Why Does My C6 Say No Fobs Detected Only Sometimes?

Intermittent messages usually point to a weak fob battery, a battery that sits low or interference from a charger or aftermarket electronics. Heat and cold can also affect a failing RCDLR. Note when and where it happens, because that's often the best clue.

Where Is the Keyless Entry Module on a C6?

High in the dash on the passenger side, above the radio, behind the trim. Getting to it means removing dash trim, so it isn't a quick roadside job.

Related Guides

• C6 Corvette Key Fob Programming
• C6 Keyless Entry Module Guide
• C6 Module Replacement Basics
• C6 Body Control Module Guide
• C6 Corvette Stuck in Park
• C6 TPMS Reset Guide
• C6 Corvette Window Indexing Guide

Sources

• GM Service Bulletin 08-08-47-001, Keyless Access System Description, Operation and Possible Customer Concerns (2005-2008 Corvette, 2004-2008 XLR), March 2008
• GM Preliminary Information PIC5961, NO FOB DETECTED Message on DIC, Possible No Crank/Start (2005-2013 Corvette, 2004-2009 XLR), February 2014, also summarized in GM TechLink
• GM Preliminary Information PIC3225J, Set Up RCDLR After Replacement (2005-2013 Corvette), 2018
• GM service information, Immobilizer Description and Operation, and Programming and Setup for the RCDLR (Corvette)
• GM parts catalog listings for receivers 25940664, 25938511 and 25971235, fob 25926480 and key blank 25995382
• RCDLR cloning and repair vendor service notes, and GM parts dealer notes on using the later fob in 2005-2007 cars
• 2005 and 2009 Chevrolet Corvette owner's manuals, keyless access and fob battery sections
• Owner reports on CorvetteForum, SmokinVette and Reddit r/Corvette (summarized, not quoted)