Glow Plug coil lights up while driving.

its a Van cargo, glow plug light is flashing, it looses or reduces speed. The brake lights both come on
Experienced mechanics share their insights in answering this question :
Hi there. The controller to the glow plugs is malfunctioning and tripping the ECM (computer) and telling it that the engine has stalled. I recommend replacing the glow plug controller / timer unit. If you need further assistance with your glow plug circuits, then seek out a professional, such as one from Your Mechanic, to help you.

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With ignition on: It is normal for this lamp to appear for a few seconds when the ignition is switched on to signify that the glow plugs are preheating. While the engine was running: There is a fault in the engine management system if the lamp appears constantly or flashes while the engine is running.
In summary, a flashing glow plug light on a diesel engine is a warning sign of a potential problem with the engine`s glow plug system. Common causes include failed glow plugs, a faulty relay, wiring issues, or a faulty control module.
With a bad diesel glow plug, as you step of the gas pedal, the engine won`t accelerate. A decrease in power can be caused by misfires in the engine, both of which are common signs of bad or failing glow plugs. The decrease in power can get so bad that the vehicle will not start at all, and you will be stuck.
There could be an issue with the glow plug circuits. Either the glow plugs have stopped working or the controller / timer has lost power. Check the glow plug relay and see if it`s energizing the controller / timer. If the relay is not clicking on, then it would need replaced.
A common car light symbol on the dashboard of diesel-powered vehicles is the Glow Plug Indicator – it comes on when the engine`s glow plugs are still warming up and your engine should not be started until this light goes out – if it flashes after starting the engine, an issue has been detected and a glow plug may have …
Bad glow plugs can hurt your engine`s performance, or cause it to stop running altogether. Unlike a gasoline engine, which relies on spark plugs to ignite the combustion process, a diesel engine is equipped with a series of glow plugs.
While you can still drive with one broken glow plug, you`ll find it extremely difficult to start your car as soon as two or more glow plugs malfunction even if the weather is warm. It`s important to note that a problem starting your car can also be a symptom of a problem in the fuel system or battery.
That`s because you will be cranking the engine in vain as you try to start it but you`ll be draining the battery of its charge. In the end, the battery will cry enough. But that`s the effect of the faulty glow plugs making starting hard, rather than the cause of the problem.
To test your glow plugs, simply connect a 12-volt test light to the positive battery terminal. Then disconnect the wires from each of your glow plugs and touch the probe of the test light to the terminal of the glow plug itself (not the wiring harness).
Faulty spark plugs and ignition coils are the most common reason for a running rough engine that causes shaking and a flashing check engine light. The shaking is usually from a misfire, and it`s common for the check engine light to flash for ignition-related codes. You might also notice a reduction in power.
The yellow coil light means your engine is too cold and when it`s warm enough it will turn off and you can start the car. If yellow coil light flashes you might have a bad glow plug.
You can drive with a bad glow plug if you have to. But the drive should be short and should take you to the mechanic`s shop. Driving on a faulty glow plug will result in continued poor performance. Eventually, your engine will misfire.
Glow plugs should last for as long as 100,000 miles; they will gradually deteriorate due to wear and tear over this period. The good news is that not only are glow plugs incredibly long-lasting, they`re also amongst the most cost-effective car parts to replace.
With the glow plug tester, you can test or have your car mechanic test steel and ceramic glow plugs on vehicles with varying on-board voltage, easily, quickly, and reliably – individually, and with no need to dismantle them or start the engine.
Start the Engine: After priming the engine, you can then attempt to start it by turning the ignition switch on and off again until it starts up. This technique should allow your diesel engine to start as long as there is enough heat in the combustion chamber to ignite the fuel.
Originally glow plugs were only used for preheating during the initial ignition. However, with modern direct-injection engines, post glow becomes more essential than ever. It allows the engine to run in a comfortable, quieter and fuel-efficient manner, even in the case of stop-start or city traffic.
How Long Do Glow Plugs Last? The average life of a glow plug on a diesel engine is roughly 100,000 miles. So, it is not something you should have to worry about very often. However, they can fail before then, especially if you hard start frequently or use a lower quality glow plug than recommended in your pickup.
The glow plug control unit uses a glow plug relay to switch the current for the glow plugs on and off. The more glow plugs monitored by a control unit, the higher the current the circuit will need. To reduce the current needed, glow plugs are often distributed across two circuits, with two glow plug relays.
Spark plugs and glowplugs should always be replaced in a complete set.
Most glow plugs require 12V, though some use other voltages. Make sure the engine is cold, and the glow plugs are turned off.
If the check engine light in your VW starts flashing, that means that the problem needs precipitous attention and your VW should be brought in immediately. This blinking light usually indicates a severe engine misfire allowing unburned fuel to be dumped into the exhaust system.
Exhaust emissions are highest following a cold start, so keeping the glow plugs on during a “post-glow” period allows the engine to meet lower emission standards. In this respect, the glow plugs act almost like spark plugs to keep the fire lit until the engine`s temperature stabilizes and emissions taper off.
Exhaust emissions are highest following a cold start, so keeping the glow plugs on during a “post-glow” period allows the engine to meet lower emission standards. In this respect, the glow plugs act almost like spark plugs to keep the fire lit until the engine`s temperature stabilizes and emissions taper off.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Shut off while driving glow plug light and check engine light on
ANSWER : Probably the simplest thing that could go wrong that would shut you off while you are driving is a loss of fuel pressure. It’s unlikely that the fuel pump would just quit while you are driving. it’s more likely that something in the control system like a fuel pump relay is shutting it down. Modern diesels depend on a number of factors to deliver fuel to the engine. Like a gas powered car, the delivery of fuel is done by electronic injectors controlled by the engine computer. If there is a failure that causes your car to stall, there is most likely a number of trouble codes stored in the computer that a technician can read to help determine what shut you down. If you contact Your Mechanic, they can send a technician to your home or office to diagnose your problem and tell you what it’s going to take to fix it.

No dash lights, back right tail light is out, no parking lights. Brake lights work though as does head lights.
ANSWER : Hi there. In many cases, when you have electrical problems like you’re describing, it’s caused by multiple electrical component failure. It’s likely that a few electrical relays are not working; especially if you have systems that utilize the same components (such as your brake light and tail lights). I would recommend having a professional mobile mechanic come to your location to complete an electrical problems inspection first, so they can pinpoint what is damaged and recommend the right repairs.

Abs light, emergency brake light, steering wheel assist light, engine light, EPC light, traction control light
ANSWER : Hello, thank you for writing in. The vehicle does utilize a lot of the same sensors for these systems. Are there any other codes that are coming up when this code appears? If so you will want to take these into consideration when processing the repair and making a diagnosis. The module may be bad, and replacing it should fix the problem. The lights should turn off once the main computer recognizes the new module and the sensors sync up. If you believe the sensors need to be cleaned you may do so. Do as minimal as possible to make sure you are not damaging the sensor or disrupting the wiring inside. A bad connection would make the lights stay on. With so many lights that are effected by the module being illuminated, the module is likely bad or does not have a connection. Check the connection first and then resort to replacing the unit. For more help with these electrical tests, contact our service department.

glow plug symbol flashing without OBDII code
ANSWER : Oddly enough, a flashing glow plug light does not necessarily mean you have a problem in the pre-glow system. It can also mean there is a fault in other aspects of engine management. Much of the information that the car can give you can be detected by any OBD-II scanner. OBD-II codes are a universal code system that all cars sold in the US have to conform to. But the manufacturers can add any number of their own specific lines of code that are not accessible to the OBD-II scanners. In a case like this, your car needs to be scanned by a VW specific scan tool, or one of the knock off’s like the Baum or the Ross Tech VAG COM scanners. I recommend having an expert technician diagnose the warning lights for you in person so that you can move forward with the proper repairs instead of replacing unnecessary parts.

Misfiring Cylinder after replacing the plugs three months ago. Is it a chance that the whole batch of plugs may have been defective?
ANSWER : Hi there. The best thing to do is switch the coil over from cylinder 3 to cylinder 1 and see if the misfire continues with cylinder 3 or if it changes to cylinder 1. If the misfire stays with cylinder 3, then either the spark plug or spark plug wire has failed. Or there could be an issue with the cylinder not sealing or getting fuel. If the misfire changes to cylinder 1, then the coil pack is not working. If you need assistance with diagnosing your misfire, then I recommend seeking out a professional, such as one from Your Mechanic, to help you

Engine light fault. There was a bad spark plug and a failed ignition coil. Replaced both the coil pack or spark plug.
ANSWER : Hi there. If the light is coming on then shutting off and returning on, then if the issue is for the same coil, there could be an issue with the wiring on the coil plug. Check the wiring on the coil plug and see if the wires are split, broken, or burned. If there is nothing wrong with the plug, then the main engine harness has an issue / short and may need replaced. If you need further assistance with your ignition system, then seek out a professional, such as one from Your Mechanic, to help you.

Glow Plug warning Light is On
ANSWER : The little orange light that looks like a spring is the Glow Plug Warning Light. But when it comes on, it doesn’t necessarily mean you have a problem with your glow plugs. Like the check engine light, it means that the engine computer has detected a fault and stored a trouble code to represent it. The car needs to be scanned by the appropriate diagnostic equipment, a generic OBDII scanner may not do the trick. By contacting Your Mechanic, you can get a qualified technician with the right equipment to come to your home or office to diagnose your car and tell you what needs to be done.

All dashboard lights and tail lights do not work after driving through a lot of snow. Headlights work. And brake lights work.
ANSWER : Hello. We’ll be happy to help you. There are a few things that I recommend checking to discover why your lighting system is malfunctioning. The headlight dimmer switch should be checked. Along with the wiring harness above the right front tire behind the fender well cover. Also
the main fuse under the hood should be inspected because other people with your particular vehicle have had similar lighting issues if that fuse goes bad. It will be a great idea to check the rest of the fuses in that area too while checking the main fuse. Once the fuses are checked inside of the main fuse box then I would check the fuses inside of their interior fuse box. The interior fuse box should be located on the driver side of the dashboard near where your legs would be. If you need more assistance with repairing your vehicle please keep in mind that our organization provides Mobile Mechanics who can help you diagnose and repair your vehicle, all at competitive rates.