How To Identify A Faulty ECU – Common ECU Failure Symptoms
Has your vehicle not been running quite right? Have you got an illuminated warning light or stored fault code and can’t work out what’s caused it? It’s possible there’s a fault with your engine ECU, or another control module on the vehicle. Don’t worry, we’ve put this guide together to help you identify symptoms of a faulty ECU, and what to do when failure strikes.
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You might already know just how important the engine ECU is to the smooth and efficient running of your vehicle. They’re responsible for a huge range of important functions, so when your ECU is faulty you’ll know about it, although failure symptoms vary from unit to unit.
Unfortunately, many of these control modules suffer from internal malfunctions which ultimately lead to a faulty ECU. In many cases, the ECU’s failure symptoms stem from the inclusion of poor quality components that degrade faster than they should do – this is particularly common in mass produced control modules. Thankfully though, as the ECU deteriorates, it tends to generate a number of failure symptoms which can help you to identify the fault.
Key signs of a faulty ECU: Engine performance
As we mentioned, when there’s a fault with the ECU it’ll cause a number of failure symptoms. Most typically, this relates to the running and performance of your engine. After all, the engine is this control module’s main responsibility – click here to better understand the role of the engine ECU.
An ECU fault can cause anything from poor fuel economy and a loss of power, to starting issues and misfires. In some cases, the vehicle may crank but never start, and in other cases the engine doesn’t even crank at all. Often when an ECU is only partially faulty, it’ll fail to carry out very specific tasks. In the case of a crank no start, although the starter motor is initiating, the engine ECU isn’t correctly controlling fuel injectors or spark plugs due to its internal fault. This is typically the case for the second-generation Ford Transit, find out more here.
Another common symptom of ECU failure is mistimed combustion. Again, this is caused when the ECU loses its ability to control or understand signals in ignition or fuel-related circuits, ultimately leading to misfires. Find out how this frequently affects the Fiat 500 here.
In more severe cases of engine ECU failure, the only symptom you’ll encounter is complete no start of the engine. When this vital control module is so severely degraded, it leaves vehicles completely lifeless. Thankfully though, this is often still rectifiable, like in the case of this widely-used Ford ECU.
Key signs of a faulty ECU: Warning lights
Aside from the aforementioned engine-related symptoms, ECU failures are synonymous with warning lights. The most frequent of which, is of course the engine warning light.
While the engine warning light is triggered by a huge range of scenarios, an ECU fault is still a possible cause of it. As we mentioned, when an ECU is faulty it might fail to carry out a function in a particular circuit. This causes a discrepancy in a signal in this circuit, which the ECU subsequently detects. Although the issue has actually been caused by the ECU, the control module senses an out of tolerance signal in a particular circuit and flags it in the form or a warning light or diagnostic trouble code.
Naturally, warning-light-related symptoms of ECU failure varies greatly, but it can be a useful early warning sign that something is wrong in your vehicle and it’s causing an electrical discrepancy. For example, a failure symptom of these Vauxhall Corsa ECUs and these Peugeot 308 control modules is an illuminated engine warning light. While these Ford Focus units trigger an ‘engine malfunction’ message on the dash and these Peugeot 207 ECUs trigger a temperature warning light when faulty.
However, it’s important not to condemn your ECU as faulty due to an engine light alone and no other symptoms. If you’ve systematically investigated all possible causes of your warning light and ruled them out, you can still send your control module off for professional testing – fill out this test form to get started.
Key signs of a faulty ECU: Fault codes
As we’ve already mentioned, a common symptom of ECU failure is a warning light or stored fault code due to an out of tolerance circuit signal. Of course, this varies greatly from case to case.
While a warning light is a very vague indicator of a vehicle fault, its accompanying diagnostic trouble code tends to provide much more context. Typically, when the ECU is faulty you’ll uncover a code with a message that relates to ‘control module error’ or ‘internal ECU fault’ - see this Citroen Berlingo ECU for example.
Alternatively, some engine control modules will generate codes specific to particular circuits, to give you a more-informed indication of the fault – like this Mini Cooper control module.
However, a regular symptom of ECU failure is that it’s rendered completely defective and loses all communication with diagnostic equipment. This is a frequent frustration for Corsa D owners. If you’re completely stuck with a no-communication ECU fault, having exhausted all possible causes, send the unit to us for professional testing to get to the bottom of your issue.
These are just some of the common symptoms of ECU failure. The possibilities are endless when these complex control modules go wrong – click here to read more.
Key signs of a faulty ECU: Avoiding misdiagnosis
Although we’ve covered some of the most common indicators of an ECU issue, it’s not always as simple as this. Each of the aforementioned symptoms can be caused by a number of issues that have absolutely nothing to do with the engine ECU or any other control module on your vehicle.
Before condemning the ECU as faulty, it’s always recommended to scan the vehicle diagnostically and rule out wiring faults. This includes checking the control module in question’s connector for poor terminal tension and corrosion.
How to resolve your faulty ECU’s symptoms
When you’ve isolated your vehicle’s symptoms to a failure of your ECU, the best course of action is to send it off for professional testing. Thankfully, we provide this very service.
Our expert technicians analyse your control module on the very latest testing rigs to identify the malfunction. Our Hardware In-the-Loop testing rigs examine your unit under realistic driving conditions to identify even the most intermittent of faults.
If we conclude that your control module is indeed defective, we’ll offer to remanufacture it for much less than the cost of a brand-new unit. We use higher-than-OEM-standard components to restore full-functionality to your unit and enhance its long-term durability.
Better still, our process takes just 2-3 working days and we’ll cover you with an unlimited-mile lifetime warranty.
Resolve your ECU’s failure symptoms the smart way, have it tested and remanufactured by the experts. Fill out our test form to get started.
How to diagnose:
Test and rebuild:
We rebuild all units with top-grade components and test them on state-of-the-art rigs to ensure they’re ready for the road when they leave us.
Programming:
All programming information is retained throughout our process, this means you can simply plug and play as soon as you receive your rebuilt unit back from us.
Quality:
We take quality seriously, this is demonstrated by our industry-leading defect rate of just 0.49%.
Warranty:
Lifetime unlimited mileage*
How do I get my unit rebuilt?
To pay for the rebuild click the Shop Now link above, select your part number and click: Get yours rebuilt.
Print the payment/booking confirmation email.
Package the engine ECU inside a sturdy box with plenty of packaging material (make sure you include your confirmation email in the box).
Send us your package by tracked courier (the shipping instructions are on the confirmation email).
Once received we will test, rebuild and return your unit with an unlimited mileage lifetime warranty. (if your unit turns out not to be faulty then we will refund your payment less a small testing fee and return shipping)
What if I don’t want to pay up front?
This is not a problem, if you prefer this option then follow the following steps:
Fill in and submit this test form.
Print the booking confirmation email.
Package the engine ECU inside a sturdy box with plenty of packaging material (make sure you include your confirmation email in the box).
Send us your package by tracked courier (the shipping instructions are on the confirmation email).
Once received, we will test your control module and call you to advise on the outcome of testing, if your ECU is faulty and you choose to go ahead with the rebuild then we will take payment over the phone using a debit/credit card.
We will then rebuild your unit and return it to you with an unlimited mileage warranty.
If you require further information regarding this engine ECU service then please contact us.