If your GMC Sierra doesn’t start, you’ve found the right article. Many different issues can cause the problem. We cover all the likely ones in an order that makes sense when diagnosing the issue at home.
This article is written with the assumption that you are looking for a way to get your GMC Sierra started now, and is meant to provide you with practical advice to help aid in the diagnosis.
First, is your Sierra cranking over at all (the engine spins when you turn the key? Or is the starter not engaging (you may hear a clicking sound)?
Table of Contents
Engine Not Cranking
Here are the most common reasons why the GMC Sierra won’t start when the engine is not cranking.
1. Battery Cables
Start by taking a look at the battery posts. If they are loose or corroded, it acts as a barrier that can keep the starter from getting the voltage it needs to crank the engine.
If there appears to be green or white on them or the terminals, cleaning them may be what your Sierra needs to get back on the road.
Here’s a good article from Napa on properly cleaning a battery terminal.
2. Low Battery Voltage
As your truck’s battery ages, its cranking amperage decreases, leaving it with a diminished capacity for starting the engine. Your Sierra needs 12+ volts to start its engine.
You can take your battery to the local parts store or even Walmart and have it tested to see if it still holds a charge.
Alternatively, you can test the battery yourself with a voltage meter. If the battery is in the vehicle and it’s under 12 volts, it’s likely bad unless your truck has been sitting for a while or something is drawing current.
If the battery is dead, it either isn’t storing enough voltage or it isn’t charging enough.
A bad alternator can cause your battery to drain to the point it can’t turn your Sierra over. Suspect the alternator if the battery light stays on after charging your truck’s battery or jumping it.
3. Starter Motor
The next thing to look at when your Sierra isn’t starting would be the starter itself. When the starter isn’t functioning, it is impossible to start your truck.
A bad starter can make a clicking noise, no noise, or it can grind.
When a starter goes bad, they will usually not give you much warning at first. Try repeatedly turning the key. Sometimes you’ll get lucky and it’ll “catch”.
Or, you can beat the starter with a hammer. It really can get that one last start out of it.
Engine Cranking, No Start
Here are the common issues that can cause your Sierra to crank but not start. Your truck’s engine needs air, fuel, and a spark to run.
It is highly likely that if the engine is cranking but not starting that it has thrown an OBDII code. Use an OBDII scanner to check and see if the engine has thrown any trouble codes.
The codes will likely be related to the potential issues listed below. When applicable, we’ve listed the common trouble code(s) associated with the cause.
1. Low Fuel Pressure
If your Sierra isn’t getting enough fuel, or any fuel at all, it may have a bad fuel filter or a bad fuel pump. Without the proper amount of fuel entering the combustion chamber, the Sierra will crank but not start.
2. Ignition Issues
One of the most significant issues that will cause a vehicle to crank but not start are ignition issues. When there is no spark, the engine will not start. You’ll probably have a misfire-related code such as P0300, P0301, etc…
Many things, including bad spark plugs, bad coil packs, bad plug wires, computer issues, and more, can cause ignition issues. It’s likely your Sierra had a rough idle before
3. Engine Timing
If the engine’s ability to fire the spark plug at the right time is called “timing”. If the spark plugs are firing at the wrong time, or something has happened to cause the camshaft to no longer be in sync with the crankshaft, your Sierra won’t start.
There will usually be OBDII codes associated with timing-related problems, but not always. P0013 is a common camshaft position-related code. The crankshaft sensor can go bad as well. When these sensors go bad, it can be impossible for your Sierra to start.
4. Security
Most modern vehicles come with smart keys that have electronic protection built in. This makes it more challenging for thieves to steal them.
There are occasions where this security system will cause the Sierra not to start, such as the key fob not working. You’ll see a security warning when trying to crank the engine, though.
5. Metering
MAF or MAP sensors measure the air entering your Sierra’s engine. If one of them has gone bad, it can cause the air-fuel mixture to be off enough to cause the truck not to start.
6. Other Issues
There are a lot of issues that can cause your Sierra not to start. That’s why it is so important to check everything. Here’s a great diagnostic chart that can walk you through diagnosing why a vehicle won’t start.
Conclusion: GMC Sierra Not Starting
There are many reasons that your Sierra may not start. Simple tests such as checking the battery with a voltage meter or scanning it with an OBD II scanner can really narrow down your list of potential causes.