The engine control module (ECM), also referred to as the engine control unit (ECU), is a critical component which links your engine to the central computer of your vehicle. The ECM manages most of the functions of the engine, based on the information it receives from other systems and electronic components within the vehicle.
If the ECM were to become damaged or faulty, then it could spell trouble for the entire engine because it would not be managed properly. If the engine is not managed properly, then it is not going to operate properly and then your car won’t work properly. You see how it all links together?
Top 5 Symptoms of a Bad Engine Control Module
If you have a bad ECM in your vehicle, the symptoms will become more than obvious. But it is important that you recognize these symptoms as they arise, so you can do something about it right away.
Here are 5 common symptoms of a bad engine control unit in a vehicle.
1) Bad Engine Performance
A big symptom that you will notice from a bad engine control module is poor engine performance. Your engine will start to have bad timing and it won’t get power as efficiently as it used to from the internal combustion process.
This will ultimately affect your ability to accelerate the vehicle as you step on the gas pedal. If you notice any kind of acceleration issues, then it could be because of a bad engine control module.
2) Engine Stalling
Along with a weak engine performance, you could actually experience the engine misfiring or at least stalling a lot. This doesn’t necessarily mean anything is wrong with the engine itself, but it does mean there could be a malfunction taking place with the engine control unit.
The engine stalling will likely be inconsistent, so it may stall sometimes and then clear up at other times. But even if you experience it one time, you should do something about it right away.
3) Bad Fuel Economy
When the engine control module is glitchy, the engine might not always know the right amount of fuel to deliver to the internal combustion process. Often times, it will start burning more fuel than usual just to sustain its normal driving needs.
This will drive down the vehicle’s fuel economy, which means you’ll be paying more money at the gas pump.
4) Check Engine Light
One of the most obvious indicators of a possible ECM issue is when the check engine light illuminates on your dashboard. This warning light could mean any number of possible issues with the engine.
If you’re lucky, it will only mean the engine control unit is in trouble and not the entire engine itself. You will need to use a diagnostic scanner to confirm what the actual issue is.
5) Car Won’t Start
If your car simply does not start and you can’t figure out why, then it may be because the engine control module has gone bad or stopped functioning completely.
You may still get your engine to crank but that’s all it will do. If the engine control unit is not working, then it won’t be able to send electronic input to the engine.
Average ECM Replacement Cost
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If you know for sure that your engine control module is not working properly, then you will need to replace it if you want to keep your car driveable.
The replacement cost of the engine control module is definitely not cheap and starts at about $600, but could go up as high as $2,000. The exact cost will mainly depend on the make and model of your vehicle. Used or refurbished ECUs can often be had at a huge savings.
The parts expense will cost the most. The computer alone is usually priced somewhere in the range of $400 to $1,600. The labor costs will likely be somewhere between $150 and $200.
So, even if you find an inexpensive (qualified) mechanic to perform the replacement job, you will still need to spend a great deal of money on the engine control module itself.
Related: Body Control Module Replacement Cost
Frequently Asked Questions
Can You Replace an ECM On Your Own?
Replacing an engine control module is generally not a do-it-yourself project for the average vehicle owner. ECMs require programming with specialized equipment only professional mechanics have access to. Without proper programming, the new ECM will not function correctly and the vehicle may not start or run properly.
ECM replacement involves advanced diagnostics to identify issues, sourcing the proper replacement part, and performing the programming procedure. This requires manufacturer-specific software and a diagnostic scan tool that home mechanics do not typically have.
There are some companies out there that sell ECMs which are supposedly flashed with the latest software and updates from the car manufacturer and are sold as “plug-and-play” products. Rarely is it that easy as the ECM must be coded to your vehicle’s VIN number.
While not impossible for a very knowledgeable hobbyist, ECM replacement is best left to the professionals.
That said, you may be able to source a replacement ECM on your own and then have a dealer or automotive electronics technician do the install and any necessary reprogramming if they agree to that. In this case, you may be able to save a couple hundred dollars but be sure to see how it would affect the warranty.
Can an ECM Be Repaired?
Yes, in some cases, an experienced technician may be able to diagnose and fix a failed component on the ECM circuit board. This involves testing the board to find faults, and then soldering or replacing individual parts.
Repairing an ECM circuit board can cost $100-$300 in labor compared to the $600-$2,000 to replace the entire ECM. However, there’s no guarantee the repair will work long-term.
Some shops offer ECM repair and remanufacturing services where they replace any failed components and update the software. A remanufactured ECM can cost $200-$500. For very old vehicles with obsolete ECMs, repair may be the only option since new replacement parts aren’t available. But again, repairs may only be temporary.
Before repairing, consider the vehicle’s age and mileage. Repairing an ECM in a 15-year-old car with 150k miles may not be worth it vs replacing the ECM or the car. ECM repair should come with at least a 1 year warranty. But an all-new ECM should come with a 3-5 year warranty.
What Causes an ECM to Fail?
An ECM can fail for various reasons. One common cause is an electrical overload, which can happen if you jump-start your car incorrectly or if there’s a short circuit somewhere in the electrical system. Be careful in these situations, as a voltage spike can damage your ECM.
Moisture or water damage is another culprit. Like your phone, your car’s ECM is vulnerable to water. Driving through deep puddles or floods introduces the risk of water seeping into the ECM and causing it to malfunction if it’s located in a certain area. Watch out for big splashes that could wet the undercarriage.
Surprisingly, low fuel quality or additives can also lead to ECM failure over time. Inconsistent gasoline grades can negatively impact your engine’s performance and the ECM by extension. Use high-quality fuels and appropriate additives to enhance, not hinder, your ECM’s operation.
Finally, general wear and tear with age can ultimately cause an ECM to fail. As with any electronics, ECMs have a finite lifespan. The daily rigors of driving will slowly degrade components until the ECM eventually gives out.
Is It Possible to Drive With a Bad ECM?
Yes, it is possible to continue driving with a bad ECM in many cases, it’s not recommended. Here’s why…
While your car may still run with a malfunctioning ECM, you’ll likely experience performance issues that can make driving difficult and potentially unsafe. For example, a failing ECM can cause:
- The check engine light to illuminate, signaling problems with the engine, transmission, or emissions. Even if there are no other side effects, you won’t become aware of other, more serious issues that would also trigger the CEL.
- Reduced engine power and slowed acceleration. Since the ECM manages engine functions like fuel injection, ignition timing, etc., it can’t properly control these systems if it’s malfunctioning.
- Poor fuel efficiency due to improper fuel delivery and spark timing. This increases gas costs.
- Stalling, hesitation, or uneven idling since the ECM regulates engine idle speed.
- Additional engine or emissions component failures may result from operating with a bad ECM too long.
While you can technically drive for a short time with a faulty ECM, it’s recommended you have it tested and replaced to avoid further (and possibly dangerous) problems down the road.
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I have a 2002 lincoln continental base sedan 4-door 4.6l. The check engine light comes on and blinks off and on. And it makes the car stall when it is going down the highway. it keeps telling me the code is cylinder 1 misfire. I have the head gasket replaced, and new plugs and coil. White smoke comes out when you first start it in the morning and it smells like oil.
i have a 2003 pontiac vibe 100000 mile starter fine one day then would start 1 time and next not scanner said 3 bad spark plugs replaced all4 scanner said error a different scanner says bad connection any idea?
I don’t know, someone will have to take a look at that one in person.
Hi Everyone,
I have a 2003 Jeep Liberty 3.7l. The jeep had an overhaul performed 1-2 years ago, and the engine was running fine. Until suddenly I stopped starting, the engine would try to turn on but i just kept doing the starting noice and never actually started. I was told by a local mechanic, that the issue was on the ECM. Perfect, I purchased one and placed it on the car, and the issue remains. The car won’t start. The mechanic is currently trying out cleaning the crankshaft sensor, but I’m losing hope in the car. Any suggestions on this?
Any engine codes? What made that mechanic suspect it was the ECM?
Hey Everyone – wondering if anyone can help diagnose what may have happened to my car. I have a 2013 VW Passat. It’s in really good shape and never had many issues with it. Check engine light was on so I plug in the code reader, turn the key in the ignition, and all the lights in the dash flash at me, followed by click, click and it won’t start at all. It was running perfectly fine an hour prior.
I just tried it again now (5 days later) hoping to get lucky but it’s all the same. Turn the ignition and all the lights in the dash flash and click, click but it says there’s an error with the brakes (?).
Does that sound like the ECM to anyone who’s more experienced with engines? Thanks for any help you can offer before I tow it somewhere to get fixed.
What was the code?
Hey friends,
I drive a 2004 nissan xterra 3.3 v6 not supercharged. I have had trouble with the check engine light for a few years now. All lights pertain to the sensors and catalytic converters. All have been replaced, some more than once and the light continues to come back on. Recently, my vehicle won’t start if it is raining/high moisture out but sometimes it just won’t start period. I also have a 16 gal tank and it won’t allow me to fully fill up and I get about 140 miles on a “full” tank. Also, performance is TERRIBLE. RPMs are generally high while trying to drive up an incline and speed rides in 40s.
My mechanic is scratching his head and I’m not in a financial position to get a different vehicle (trust me I wish I could).
Any thoughts or has anyone had experience with this vehicle or these issues?
Thanks
Lacy
Good morning friends. I drive a 2008 Hyundai Elantra. I recently changed the pistons and rings (total engine overhauling). I didn’t get a better engine sound in the end.
That’s not the main issue. The car is now having issues starting. Sometimes, it could go off in the middle of the road. Recently, an auto electrician checked on it and was able to start the car.
But the ECU gets so hot that I am afraid to drive it around.
Is it normal for the ECU to get so hot? I mean very very hot
Double check your grounds, make sure all are clean and tight. Did your auto electrician have anything to say about the ECU temperature?
04 5.9 cummins diesel stop;s running when temp gets to operating range then shuts off,will start again but then stop,s again installed new fuel system,replaced injector pump,new fuel soilanoid, checked fuel presser,been told it could be the ecm,dont know where to go from here
Try cleaning your mass airflow sensor.
Thanks,Sean I checked it its clean,however that doesn’t mean it’s not faulty.I sent the ecm off to have it checked and if it comes back good im at my end.The truck only has 70K on it.
Yeah it could be faulty, I don’t know. If it were me in that situation I’d pay the $150 bucks or so for a good diagnosis. It’d save me the trouble of having to go back and forth trying different parts. Good luck, hope this helped.
I have a 2008 sub 97X I jumped another vehicle with it and now my car won’t start it will crank and I can hear the fuel pump coming on and it’s getting 12 volts to the ECM could ECM still be junk I can communicate with the ECM
Hi.
I have a Jetta 2002. Engine light on and a glow plugs message for all 4 cylinders. Changed glow plugs with no change. Ended up changing ECT sensor, but nothing.
Now with the sensor unplugged, glow plugs works for 20 seconds and it starts fine. But the gauge temp. on the cluster reads 0 degrees all the time.
If I plug the sensor back, still no temp. Readings but now back to glow plugs not getting any voltage, And car does not start.
What is left to check before getting to the ECM?
Thanks
Great stuff, thanks. Considering buying an 11 year old Lexus with 44,000 miles. In its last service, the owner stated the car wouldn’t star with the push button, just the key starter. Mechanics reported there were no codes flashing pointing to the problem, and starter the car each time with the button that day without problems. Car sat overnight and started again 100% of the time. Mechanic wonders if steering lock is an issue. I am wondering if the owner’s experience shows the ECU is starting to fail. Could it be?
Unlikely to be the ECU. Have you checked the key fob battery?
Hiii , I have Datsun go
When I on the ac it starts sacking, it happens only when ac is on , and becomes normal after ac off, and sowing error of emu and cylinder 1 misfire
What may be the cause,.
I have a 2008 Saturn aura and I noticed the dash needles bouncing and the car slow to accelerate and my fuel economy at 13.3 mpg on the highway. I got the codes read and it said lost comm to ECU and TCU? Would replacing the ECU help?
Not sure. If the problem is inside the ECU or TCU, it’ll help. If the problem is with a bad ground or inside the wiring harness somewhere, it won’t help. You’ll have to do some electrical diagnostics to figure out where the issue is. Weigh the cost of an electrical diagnosis against the cost of a new ECU and TCU. Chances are good that the electrical diagnosis will be worth the money.
I have a 2005 Hyundai Tucson and the problem i’m having is high RPM (up to 4000) it surges on me when i go from reverse to drive and after driving around stopping and starting at different places the car will not restart, I wait about 15 minutes and then it will right up. All these problems are random so really hard for the mechanics to figure out when I bring it in. I’ve had the air idle control replaced and did not change a thing. I’ve replaced spark plugs and wires and still no change. Just got it back from the shop and was told they suspect the ECM. Other than these problems the car runs great. Any thoughts.
Could be the ECM, I don’t know. I’d try to monitor fuel delivery when that happens (specifically the fuel trim parameters) to see if that gives you any clues.
Months ago I started getting a “low oil pressure” warning on my dash screen. Once idle picked up after stopping at a light, it went away and wouldn’t happen but a few more times or so per day. Didn’t think anything of it until one day when the truck went into limp mode after many warnings came on the dash screen starting with low oil pressure, engine hot, advance track fail, check 4×4, and a wrench popped up. I pulled over, turned off the truck, waited a few moments, started it up, and was back on the road driving again with no issues. This sequence of errors started happening a little more frequently over the next few weeks until one day, it would not start again. No crank, no start, just the same error messages cycling thru on the dash screen. The truck would NOT retain any of the error codes for a scan tool to pick up on prior to it not starting again. After hooked up to a diagnostic machine, the ECU was not found. All other modules were discovered except for the ECU. After ordering a replacement ECU online and having it programmed to my VIN number, as well as the PATS reprogrammed to my existing keys, the truck did start a few times, but the next day when I went to drive it, it was dead again. I repeated the process, got another programmed ECU, and it did the same thing, started a few times, and then it was dead again. The speedometer would show up as dashes only, no miles. I had all fuses and relays checked, both in the engine fuse box as well as the BCM fuse box in the cab at the passenger side foot panel. All fuses checked out fine. We opened many places along the engine wiring harness to inspect for chewed or damaged wiring. None were found anywhere. I’ve had a mobile ford Tech look at it as well as a wiring harness rebuilder but both were unable to locate any reason for new ECU’s to be crapping out after a few start up processes. It seems like there is a short somewhere, but no one is able to locate it. Does anyone know what could be causing the ECU to blow repeatedly and make it OBDII undetectable after it goes out? The dealer is my last hope and before I go there and get lubed up, I just wanted to see if anyone may have something else for me to try. Thanks.
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Sounds like you’ve done a pretty thorough diagnostic so far. The only thing I would recommend is to check forums to see if this is a common issue on your truck… or if maybe there is a common engine ground that tends to get soiled. For instance on the first gen Silverado there is a ground next to the driver side frame rail. This ground often gets dirty and corroded because it’s right in the path of the tire as the tire sprays junk from the road. This can cause issues with the ABS module if there isn’t a solid connection.
I have a new computer but the car still don’t crank what is the problem
It’s possible the computer wasn’t the cause of the no start condition. Have you tried anything else so far?
Hi i have an issue with my 2010 dodge journey. It has been playing up for about 6 months but now its getting as bad as me havibg to jumpstart it mpst mornings because my battery is drained. Its a new battery a few months back. Also i can sometimes hear a clicking noise coming from underneath the fuse box. Definatly not the fuse box itself because had it chacked by mechanic. My horn honks randomly, stalls or is about to stall in 3rd and 4th gear idling in a 50km zone. engine light comes on every now and then and my traction control thinks the front left wheel is going 10kms quicker than the rest of the wheels. Do u think its the ecm? And if it is can i buy a cheaper part to bypass it? The transmision is not the best so dont want to pour loads of money into a dud
It sounds like an electrical short somewhere or maybe a bad ground. I wouldn’t be quick to blame the ECM, I think you need a professional diagnosis before you should try to replace anything. No, you can’t bypass the ECM. The ECM is the computer that controls the engine.
Is a 2009 Jaguar 4.2ECM compatible with a 2010 Jaguar 5.0
I don’t know. I think it’s very unlikely that they would be compatible, but you can probably double check this on the Jaguar forums.
I have a 2005 Honda Accord V6. It started to idle rough randomly, then had a flashing check engine light. Code read out misfire on cylinder 5. Replaced the coil pack and all spark plugs. Car ran great for about 4 days, then rough idle, check engine light, and code that read misfire on all cylinders. Took it to a mechanic and the only thing they found was that the brand new coil pack had already gone bad. Replaced it again and it ran great for almost two weeks. Started the car this morning and, you guessed it, rough idle and check engine light. Have not read the code yet. It has been suggested to me that it is likely the ECU. Anyone have any thoughts before I spend $1500 on a replacement?
Yes, I would do some more digging before replacing the ECU. It sounds like there may be something that is shorting out or overheating the coil pack. When this type of thing happens, the coil pack can go bad much faster than it is supposed to. Change your spark plug wires if you haven’t already, then check and clean all engine grounds.
Yes that’s exactly what happened with my car
I have a opportunity to buy a Chrysler Sebring 2008 and the ecm is going bad would you recommend me buying the car for 1500
If you can fix the issue yourself, you know your limits and what you’re willing to pay to fix a mechanic’s special. If you’d be taking the vehicle to the shop, I’d keep looking for something else.
I park my truck and go to bed in the morning the interior light is on and it sounding I close the door and the dashboard tells me that the door is adjoua what could be the cost
New battery ( put in 5 months ago) used altnator ( put in 5 months ago) car runs drives but ” battery savor mode” keeps coming on about 30 second after i start my car under my message center . after running for 5 minutes then the battery light comes on too.
No check engine light, starts with no problem. What can this be?
2012 Dodge journey
Hi Anna was wondering if you solved this issue.
My battery was changed, alternator changed and still battery stop light showing.
Any guidence would be great as mechanic is stumped
Will this make check engine light come on and blink off and on.it keeps telling me the code is cylinder 3 misfire and ive replaced plugs wirs coils and icm could it be the ecm is going out.
It could be, but it’s probably not the ECM. It could be a clogged injector not getting enough fuel to one cylinder. You could pull the injectors to have them tested or cleaned.
Perhaps you have poor compression in that cylinder? You could perform a compression test to rule that out too.
i finally found a intermittent misfire and come to find out it was the number 1 and number 4 cylinder leaking coolant into the combustion chamber from a bad head gasket, luckily it wasnt in the oil so i could use the vehicle up until i could finally afford replacing the head gasket myself, and if that might be your problem then i would suggest having the heads resurfaced, its dirt cheap and worth it either way.
Good luck man, i hope you find the issue soon and at low cost….
Hey my brother Sean. Just wondering if you would have a clue what’s wrong with my bmw 320i 2007. Engine light come on saying coils n sparks I’ve now replaced dem w brand new sparks n coils now codes are saying misfire in cylinders? Cars rough idling. Just seeing f you would have any idea please before spending on a new ecu
Hey Gerald. Plugs and coils were a good start, but there are a couple more things you can check. Using a scan tool, can you check what the air fuel ratio (AFR) and fuel trims are? If those are lean, you may want to do a fuel pressure test and start troubleshooting the different fuel system components.
If everything looks normal on the scan tool (or something is obviously wrong with one cylinder), you may want to perform a leak down test. This is similar to a compression test, but will tell you if you are losing compression through the valves, piston rings, or cooling system. If you’re losing compression through the cooling system in one or more cylinders, you may have a head gasket leak.
Mahalo! Very informative!