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

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.


Next Step

Schedule Warning Light is on Inspection

The most popular service booked by readers of this article is Warning Light is on Inspection. Once the problem has been diagnosed, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. YourMechanic’s technicians bring the dealership to you by performing this job at your home or office 7-days a week between 7AM-9PM. We currently cover over 2,000 cities and have 100k+ 5-star reviews... LEARN MORE

SEE PRICING & SCHEDULING

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Recent Warning Light is on Inspection reviews

Excellent Rating

(199)

Rating Summary
187
5
4
0
3
187
5
4
0
3

Jason

15 years of experience
344 reviews
Jason
15 years of experience
Nissan Armada - Warning Light is on - Mineola, New York
Excelente. Jason es todo un profesional con mucho conocimiento en la mecanica, buena persona educado y amigable. Gracias Jason.
Ford Taurus - Warning Light is on - Jamaica, New York
Very Professional definitely takes his time to find out exactly what’s the problem with the car! I was up and running in no time ! Will definitely recommend Him to anyone having issues with cars!!!

Travis

13 years of experience
497 reviews
Travis
13 years of experience
Volkswagen Beetle - Warning Light is on - Stillwater, Minnesota
Unbenoest to me when you change a battery on a 18 yr. old car you also need more than a code reader to reset the new battery.
Audi A8 Quattro - Warning Light is on Inspection - Minneapolis, Minnesota
Very helpful and very knowledgeable will be using this service again thank you Travis for everything trumbs up

Nicholas

11 years of experience
472 reviews
Nicholas
11 years of experience
Chrysler 300 - Warning Light is on - Durham, North Carolina
Excellent diagnostician. Knowledgeable and caring. Created a desire for him specifically, to do the job. Hope we get him every time!
Honda Accord - Warning Light is on - Garner, North Carolina
I was very happy with Nicholas and his knowledge and expertise about diagnosing the issues with my car. He is honest, reliable and professional. He is now my Mechanic that I will call on for all my car's needs.I will also recommend him to my friends whom have been taken advantage of by other car shops as I have been, and are looking for someone honest , that will not take advantage of them Thank you so much Nicholas for resolving my issue with my car. I feel relieved and happy with the outcome

Eduardo

19 years of experience
457 reviews
Eduardo
19 years of experience
Chevrolet Equinox - Warning Light is on Inspection - Houston, Texas
He arrived way early take his time and ran his diagnostic and i was satisfied at the end of his work great job

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

Related articles

The 10 Most Important Things in Your Car Owner’s Manual
Your owner's manual tells you important information about your car, like how to set up your car, how to check car fluids, and correct tire pressure.
How to Replace the Glow Plugs in Your Car
Car glow plugs work hard to regulate temperatures to help diesel engines run. Glow plugs often wear out and need to be replaced.
The 10 Transmission Problems to Never Ignore
There’s nothing quite like transmission problems to stress out the average car owner. They are, at best, inconvenient and, at worst, very expensive. Proper...

Related questions

After jump-starting, warning lights came on

If you are having random electrical problems that don't seem to be related to the car not starting, it is likely that you have an alternator failure with your Mercedes E500. When an alternator fails, it can cause all sorts...

Wrench light on dash after tune up and throttle body cleaning.

Hello there, many faults will cause the wrench light to be seen in your 2010 Ford F-150. When the throttle body was cleaned if too much cleaner gets on the throttle body sensor or into the throttle motor, then this...

All my dashboard lights come on and my car stops and won't let you continue until you shut it off and on again

Hello, thank you for writing in. The warning lights and loss of power that you are having are typically triggered by a major malfunction. The braking and unresponsive throttle are both safety features to keep the vehicle from putting you...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com