Aston Martin DBS/DB9 in Limp Mode with P2106? Why It’s Not Always the Throttle Body

Your Aston Martin DBS or DB9 suddenly drops into limp mode. The throttle response feels like you’re pushing through wet concrete. The check engine light is on, and your scanner shows P2106 – Throttle Actuator Control System – Forced Limited Power.

Most people immediately blame the throttle body.

Sometimes they’re right. But on modern Aston Martins – especially V12 cars with dual ECUs – P2106 can be a symptom, not the root cause.

In this article we’ll break down:

• What P2106 actually means

• Common mechanical causes you should rule out

• When to suspect deeper ECU or immobilizer issues

• How UpFix helps shops and owners get these cars out of limp mode for good

What P2106 really means

P2106 is a “torque management” or “limp mode” code. In plain English, it says:

“The engine computer detected a serious problem and is intentionally limiting power.”

On Ford-based platforms (including many Aston Martins), it can be set because of:

• Throttle actuator faults

• Throttle position sensor disagreement

• Airflow or torque errors

• Certain transmission or driveline faults

• Severe misfires or fuel issues

• Security / immobilizer problems that make the ECU cut power

In other words, P2106 tells you the ECU has pulled the plug, not why.

Step 1: Rule out the obvious mechanical issues

Before you dive into ECU diagnostics, you should always check the basics. On a DBS or DB9 with P2106:

1. Inspect both throttle bodies

   • Check for carbon buildup, sticking plates, or physical damage

   • Verify connectors and wiring for corrosion or broken pins

2. Check for related throttle codes
   Codes like P2101, P2110, P2112, P2118 etc. can point to direct throttle actuator or position sensor faults.

3. Look at live data

   • Do commanded and actual throttle angles match?

   • Do pedal position sensors 1 & 2 agree with each other?

4. Check coils, plugs and misfire counters
   Severe misfires can cause the ECU to limit power.

5. Inspect PCV and basic air path
   Vacuum leaks and crankcase ventilation issues can cause strange airflow readings.

If all of that checks out – or you’ve already thrown parts at those areas without success – it’s time to think like an ECU.

When P2106 points to deeper ECU or immobilizer problems

On V12 Aston models with dual ECUs, P2106 often shows up as part of a larger pattern, not as a single isolated issue.

Here are red flags that suggest a control-module problem:

1. One bank runs, the other is cold

If you have:

• One exhaust that gets hot

• The other exhaust staying cold or just warm

…and live data for Fuel System Status shows one bank at “0 – No Fuel” while the other behaves normally, that’s a strong clue that one ECU is not enabling fuel.

This is exactly what we saw in Sam’s 2011 Aston Martin DBS case. The left bank behaved normally; the right bank looked like fuel was shut off at the ECU level.

2. Limp mode plus key/immobilizer warnings

If swapping or disconnecting ECUs leads to “key mismatch”, “immobilizer active” or similar security errors, that’s another big hint.

It often means:

• A previous shop replaced one ECU with a used unit

• The VIN and basic calibration were programmed, but

• The immobilizer / key data wasn’t properly cloned

The car may start and run, but the security system isn’t fully happy. Under certain conditions, it can:

• Command limp mode (P2106)

• Disable fuel on one bank

• Randomly refuse to start

3. History of ECU replacement or “programming”

Any time you see:

• Tape or marker writing on an ECU case

• Part numbers that don’t quite match the other side

• Service records mentioning “reflash” or “cloned ECU”

…you should treat a P2106 limp mode complaint as partly an electronic/data problem, not just a hardware problem.

Why VIN match is not enough

Many shops think: “If the VIN in the ECU matches the car, we’re good.”

On Ford-based Aston platforms, that’s only part of the story.

ECUs also store:

• Immobilizer / security data

• Key information

• Checksums and other internal consistency values

If you program only the VIN and calibration into a used ECU but leave the security section mismatched, you’ve created a time bomb:

• The car might start, but fuel can be cut later

• Swapping ECUs side-to-side can trigger a “key mismatch” no-start

• P2106 shows up as the ECU’s way of saying “I don’t trust this situation”

A real-world example: the DBS that wouldn’t play nice

In Sam’s Aston Martin DBS case:

• The car had P2106 and limp mode, with extremely slow throttle response

• The right exhaust stayed cold, and live data showed no fuel on that bank

• After swapping the ECUs, the car threw a key mismatch and wouldn’t start

When the modules arrived at UpFix:

• Both ECUs communicated on the bench

• Both showed the same VIN and calibration

• But deep memory analysis revealed that the immobilizer blocks didn’t match

Someone had clearly tried to replace or clone an ECU in the past – they just didn’t finish the job.

We fixed it by cloning the correct immobilizer data from the good ECU to the replacement, turning them into a properly matched pair. Once reinstalled, the DBS could run both banks without limp mode, and P2106 disappeared.

A practical diagnostic checklist for shops

If you’ve got an Aston Martin DBS or DB9 with P2106 and limp mode, work through this checklist:

1. Check and clean both throttle bodies

   • Mechanical movement

   • Connectors and wiring

   • Related throttle actuator codes

2. Verify coils, plugs and misfire status
   Fix obvious misfires first.

3. Compare bank-to-bank behavior

   • Exhaust temperatures

   • Fuel system status per bank

   • Injector command and pulse width

4. Ask about ECU history

   • Any prior replacements?

   • Any non-factory programming or tuning?

   • Mismatched part numbers or labels?

5. If one bank is “no fuel” and immobilizer errors appear, stop guessing
   At that point, you’re likely dealing with:

   • A failing ECU driver, or

   • A security/immobilizer mismatch between modules

That’s where UpFix can save you a lot of time and your customer a lot of money.

How UpFix helps with P2106 and ECU-related limp mode

When you send ECUs to UpFix for an Aston Martin in limp mode:

• We bench-test both ECUs (left and right)

• Verify VIN, calibration and immobilizer data

• Repair hardware faults where possible

• Clone or correct immobilizer blocks so the modules agree and the car trusts them again

• Provide tech notes you can reference on your RO or in your YouTube video

Instead of throwing more throttle bodies, coils or “good used” ECUs at the problem, you keep the original electronics in the car and fix the root cause.

You also help keep expensive modules out of the landfill – repairing and reusing electronics is almost always more sustainable than replacing them.

Stuck in limp mode? Don’t guess, test.

If you’re looking at:

• An Aston Martin DBS or DB9

• Limp mode with P2106

• One bank cold, “no fuel” status

• Key or immobilizer errors after an ECU swap

…it’s time to get the ECUs professionally tested and repaired.

📞 Call UpFix at 888-979-9343 or visit UpFix.com to start your repair.
Send in both ECUs, include a note with your scan data and symptoms, and we’ll let you know exactly what’s going on – so you can get the car out of limp mode and back on the road.