Cooper S R55

liora_zabalaz · Post by **liora_zabalaz** » Wed Jun 17, 2026

Good day,
I am experiencing a 2008 R55 Clubman Cooper S and am perplexed by the DTC misfire codes and flashing EML. I am trying to determine the source of these issues.
We can attribute the codes to a Topdon scanner.
2978 Engine Fires, Multiple Cylinders 277D Engine Fires, Second Cylinder 2775 Engine Fires, Third Cylinder

The engine control unit (ECU) was rebuilt at ECU Testing in Derbyshire, and the vehicle has received new plugs, injectors, coil packs, and other mechanical parts.
I verified the fuel pressure using real-time data, and it is correct.
If you keep the engine revved up to 3000 rpm for around 15 seconds, the EML will activate and the live misfire count will go to zero, but I still can't tell if it's misfiring.

The vehicle first experienced issues when it entered limp mode, reduced its engine power to three cylinders, and displayed the code 2D7F, which stands for open circuit injector 1.
I made sure the wiring was intact and checked the injectors for resistance and actuation. Despite finding nothing wrong, I decided to change the injectors while they were out because the car has logged 135 thousand miles.
After finding that the ECU had already been repaired, I had it rebuilt by ECU testing in Derbyshire, who now offers a lifetime warranty.
I am at a loss as to what to do next; after reinstalling the intake manifold and injectors, I am getting misfire codes for cylinders 2 and 3, but there is no obvious misfire.
What I haven't done nearly as much as take everything apart and switch out the injectors to see if the codes shift to cylinders 1 and 4, indicating that the injectors are to blame....

liora_zabalaz · Post by **liora_zabalaz** » Wed Jun 17, 2026

It has also undergone a timing chain within the past five thousand miles.

mirabelnordstromci · Post by **mirabelnordstromci** » Wed Jun 17, 2026

Perform a smoke test on every cylinder by closing all four valves; observe for the presence of smoke emanating from the intake or exhaust ports. Notice the tail sign that indicates common valve seats are dirty or that there is a significant buildup of carbon crud on the intake valves.

liora_zabalaz · Post by **liora_zabalaz** » Wed Jun 17, 2026

I appreciate it and will give it a go. However, I fail to understand why these codes would appear after resolving the injector no. 1 open circuit; they were previously absent.

mirabelnordstromci · Post by **mirabelnordstromci** » Wed Jun 17, 2026

I'm starting to wonder why the ecu was spiked in the first place; I've fixed the result, but not the cause. Here are a few things you need to know: the battery is good, the alternator is tripping over 14 volts when the engine is running, it's common for thermostat failure to pull the drivers down in the ecu, and the engine doesn't always give me codes. Sometimes diagnosing these engines sends me on a wild goose chase, haha.

liora_zabalaz · Post by **liora_zabalaz** » Wed Jun 17, 2026

Thank you for bringing this to my attention. I will investigate the alternator further; perhaps its output will shed light on why the EML turns off and the misfire count goes to zero when the engine is held at 3000 rpm for approximately 10 seconds.

mirabelnordstromci · Post by **mirabelnordstromci** » Wed Jun 17, 2026

I'll add that I've experienced coil packs failing, which pulls the ecu south. Another common issue is when the 02 sensors short circuit or have a high resistance, which similarly pulls the ecu south. On pre-2010 vehicles, the orange wire is the common wire; it sends 12v to the oil solenoids, thermostat, heater circuit, water pump, jockey wheel, and coil. The ecu then uses an earth wire, also known as "switched earth," to turn these components on and off.

mirabelnordstromci · Post by **mirabelnordstromci** » Wed Jun 17, 2026

This is highly probable; I have an 80k-mile 2019 Transit Custom with a misfire that occurs both at full load and at idle, with the alternator drawing the least power. The misfire occurs at idle and surges when I drive uphill. I monitored the data and found that the voltage dropped from 13.6 to 12.9 volts when the misfire occurred. The ecu is designed to flow 14.2 to 14.7 volts, so when it falls below this, it cannot provide the drivers with enough power to operate the injectors. I can tell it's not the same because it's ford and diesel, but it could be

liora_zabalaz · Post by **liora_zabalaz** » Wed Jun 17, 2026

I have checked the battery voltage while the engine is running and it is consistently 14.4 volts, but the scanner is showing a range of 13.7 to 13.94 volts, which is likely coming from the electronic control unit (ECU).
When the OBD port is connected, the scanner will display a voltage reading of 13 to 13.7 volts.
The voltage jumps from 12.45 to 14.4 volts when you start the car, so I'm thinking the alternator is charging.
My battery is dead.

mirabelnordstromci · Post by **mirabelnordstromci** » Wed Jun 17, 2026

Indeed, the charging is occurring at the expected location.