What Does the Diesel Engine Pre-Glow Warning Light Mean?

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Due to the nature of diesel engines, they require some extra help when first starting up at a cold temperature. The glow plug is a heating element that is activated during startup when the temperature of the engine is too low. It raises the temperature inside the cylinders to facilitate in pressurizing and detonating the diesel fuel. The system typically makes the driver wait around 10 seconds while the plugs warm up the engine. Once the correct temperature has been achieved, the computer will then let the driver start the engine.

What the diesel engine pre-glow light means

Normally, the glow plug indicator light will come on only when the engine is cold. Typically, this light flashes only when an issue has been detected.

The most common reason to replace glow plugs is age. Over time, after repeated warm up cycles, the glow plugs age and are not able to produce any heat. Replacing any malfunctioning glow plugs should get rid of any issues you are having. If a new glow plug doesn’t remedy the problem, take a look at other parts of the circuit, mainly the timer. The timer’s job is to turn the plugs off once the correct temperature has been reached. A faulty timer may keep the plugs on for too long, wearing them out, or even not turn the plugs on at all.

If a fault has been detected, the computer will save a code in its memory to help diagnose the issue. Have a certified technician hook up a scan tool to your car to read this code.

Is it safe to drive with the diesel engine pre-glow light on?

Some vehicle engines cannot even be started until the glowplug light has turned off, therefore preventing the drivers from starting the engine too soon. You should always wait for the light to shut off before attempting to start the engine. Being a little patient will help keep your engine going strong in the long run.

Our certified technicians are always available if you ever require assistance identifying glow plug issues.


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Matthew

32 years of experience
704 reviews
Matthew
32 years of experience
Chevrolet Impala - Warning Light is on - Norfolk, Virginia
First off he was on time....actually 30 mins early which was great. Everything he described was what I was going through and he knew exactly what I needed before he even looked at the car. Other mechanics i feel were trying to take advantage because I am a woman but he made me feel comfortable. Still have to get work done on it but at least I know exactly what the problem was.
Chevrolet Tahoe - Warning Light is on - Norfolk, Virginia
Very detailed and takes the time to explain what is being done. Willing to answer any questions you may have. I would definitely use his services again and have already been telling my coworkers about this site. I have a unique electrical situation going on with my truck that none of the dealers could assess. Just by Matt doing some general maintenance , my truck is already driving smoother. Matt asked that I monitor things to make sure we don't need to troubleshoot anything else. I feel quite confident.

Quentin

18 years of experience
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Quentin
18 years of experience
Volkswagen Tiguan - Warning Light is on - Nottingham, Maryland
Quentin was very professional and meticulous with locating the issues with my car. Great spirit and explained and answered all of my questions.

Travis

12 years of experience
69 reviews
Travis
12 years of experience
Mercedes-Benz C230 - Warning Light is on - Charlotte, North Carolina
Travis came out to determine cause for the Check Engine light. He did so and told me what needed to be done and the cost.

Juan

8 years of experience
50 reviews
Juan
8 years of experience
Suzuki Grand Vitara - Warning Light is on - Durham, North Carolina
I won't go into details about the actual work performed - the result was completely satisfactory. Juan is knowledgeable about how these computerized engines work . He's very personable, polite, patient with my questions, and when I need service again, I'll request Juan. He put in more time than originally scheduled and seems to want to see things through and honest enough to tell you if the job is beyond his expertise and suggests taking car to dealer for more extensive diagnostic tests. I am well pleased.

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