Misfire Correction (Coast Down) Procedure DIY Guide
DISCLAIMER
As always, follow all safety protocols. Don't undertake this task if you aren't comfortable with it, fully understand it, and are capable of completing it. The information provided may be incomplete or inaccurate. You are ultimately responsible for anything you do. Neither Redpants, LLC or myself is responsible or liable for anything that may occur.
One of the most common “problems” that pops up with Gaydon-era Aston Martins in the emissions warning and accompanying check engine light (CEL). Another issue that’s far more concerning but not as frequent is that the engine can sometimes stall for seemingly no reason when the car is coasting. Turns out, there may be one underlying factor that’s causing both: misfire correction data.
The factory guidance for this is detailed in Service Bulletin SB-30-0313, which superseded SB0193. It includes steps that require an AMDS. If you’re reading this, it’s a safe bet that you don’t have one of those, so I’ve revised the steps to exclude those that include it.
This procedure needs to be done if:
The Powertrain Control Module (PCM) has been replaced or reprogrammed *(see Note below)
The “Keep Alive Memory” was lost after a battery replacement or disconnection *(see Note below)
If any of the following where replaced:
- The Transmission Control Module (TCM)
- The Engine Management System (EMS)
- The flywheel, clutch, or auto flex plate
- The engine speed sensor (just the rear sensor on V12 engines)
- The transmission
- The Mechatronik unit in the transmission
- The engine or important engine hardware like the crankshaft, pistons, camshafts or cylinder head
Note: Vehicles from MY10.5 onward will not lose their misfire correction factors if:
The Powertrain Control Module (PCM) has been reprogrammed, or,
The PCM has lost its “Keep Alive Memory” after a battery replacement or disconnection.
So long as these procedures are done correctly, the vehicle should have correct misfire detection, fewer instances of emissions warnings and check engine lights (CELs), improved drivability, and smoother gear changes.
Needed
OBDII tool with correct software (optional)
- Foxwell NT530
- Foxwell NT710
Long, open, high-speed road
About 20-30 minutes
Before you begin
It’s commonly said that an additional restriction when doing this procedure is that the steering wheel can’t be turned more than 10 degrees. The steps listed in this DIY Guide are based on Service Bulletin SB-30-0313 which does not mention the steering angle restriction. However, if the procedure isn’t working, it may be due to steering inputs.
An OBDII diagnostic tool with the correct software may be able to help determine whether or not the procedure has worked. The Foxwell NT530 and the Foxwell NT710 sold by Redpants are pre-loaded with software for Aston Martin, including this functionality.
Step 1
Fully warm up the vehicle to normal operating temperatures. The engine coolant should be at least 185F (85C) and transmission fluid should be between 122F and 212F (50C to 100C).
Step 2
Set the air conditioning (A/C) and Sport mode to Off.
Note: The procedure will not work if the A/C or Sport mode are in operation.
Step 3
Drive the vehicle and increase speed to a constant 70 mph (110 kph). The transmission must be in 6th gear (in D or ASM mode for a Sportshift car, or 6th gear for a manual car).
Step 4
Fully release the throttle and let the vehicle coast down to 30 mph (48 kph). Do not use the brake, gas, or clutch pedals, or the hand brake during this time.
Note: Steering angle may also be limited to less than 10 degrees of input.
Step 5
Repeat Steps 3 and 4 two more times.
Step 6
If the procedure was done correctly, the misfire corrections will be stored and you’re all set! An OBDII tool with the correct software may be able to confirm the corrections were learned.
If not…. start over from Step 1.
If you have an automatic transmission (not Sportshift), then you’ll also need to do the Automatic Transmission Control Module (TCM) Adaptive Learning Procedure.
WARNING
Full completion of this DIY Guide includes driving at 70 mph (110 kmh) and allowing the car to coast without any input from the gas pedal, clutch pedal, brake pedal, handbrake, and potentially steering wheel. Do not attempt this where such speeds are not safe or legal.