Does anyone know what Fault Code P2073 - Throttle Position Correlation means?

I have noticed that when accelerating in third or fourth gear above 3,000 RPMs the RPMs suddenly jump to 5,000/6,000 RMPs or so without me pressing the throttle. Have anyone ever experienced this problem/know the fix? This is on a 2011 V12 V manual.

Thanks all in advance!

 

P2073 is a generic OBD code indicating that the amount of intake air mass signaled to the DME/engine management computer to be passing by the “Mass Air Flow” sensor (MAF—the sensor that measures how much air is being pulled into the engine, allowing the engine management to calculate how much fuel to inject, etc.) does not correlate with what this computer expects given a specified throttle plate position. Essentially, the amount of air measured to be going in doesn’t match what the computer expects. There are a variety of possible causes—a bad signal or faulty measurement data due to a defective MAF sensor, or signal wiring circuit, or a true condition where the incoming mass does not correctly correlate (air is leaking in due to a vacuum leak at the intake manifold, etc). Fault frequency and standard diagnostic procedures will pretty quickly establish the cause one way or the other and indicate whether the fault is mechanical or electrical/signal related.

A quick search indicates that this generic OBD code appears to be specific to idle conditions only. If this is indeed the case, it is unrelated to your experience of the engine winding up under acceleration as you have described. Since you are not working with an AM manufacturer diagnostic code, but rather a generic OBD code, the code itself might not have the same resolution of a manufacturer’s fault code (ie what an AMDS would indicate) so I wouldn’t immediately assume that it is at idle only. I assume the check-engine-light is on related to this code—are there any others? Did the light turn on at the same time as the unusual engine “revving” phenomenon took place?

When the engine rev’s, can you verify whether you hear engine speed increase (want to eliminate a gauge error)? If the engine does indeed increase in speed, can you verify whether the car accelerates at an expected rate per this increase in engine speed?

Generally speaking, the phenomenon you describe is that of a slipping clutch (engine speed winds up under load without commensurate acceleration because the engine’s torque cannot transmit to the driveline as a result of a worn/slipping clutch.) If the OBD code is not only applicable to at-idle only condition, it would be expected to get this sort of correlation code with a slipping clutch friction-plate.

 

Thanks for the reply. No, there are no lights on the dash. Yes, the engine does speed up when the phenomenon happens. When it happens the car appears to accelerate abruptly as if the accelerator is depressed and the car has a mind of its own.

 

Interesting!

Have you cleared the MAF code to see if/when it returns?

Best case scenario that code represents a very minor anomalous deviation and there is only one or two instances over a period of time. I have seen similar codes tripped by very dirty intake filters, and often by a change to a “cold air intake”, or the installation of a “performance” air filter assembly.

More concerning is that the car actually accelerates on its own with zero driver input. I have never encountered a real scenario where this has taken place on a drive-by-wire car. There are many sensors and equipment present to prevent this phenomenon. Two thousand RPM in third or fourth gear is what? 20-30mph increase in speed? How replicable is this phenomenon? How many times has it happened? And to confirm, the car does indeed accelerate at the same MPH as you would expect for that increase in RPM? I am really trying to rule out a slipping clutch.

Drive by wire systems rely on sensors. There are two on the accelerator pedal, and at least one sensor at each throttle body (V8 has one TB, V12 has two, often times drive by wire cars will have an additional one or two sensors to compare signals so that the scenario you are describing is made impossible—car immediately goes into “limp mode” as soon as there is any deviation in correlation between any of the sensors signal, preventing unwanted acceleration). The DME/ECU takes the signal from the accelerator pedal (sensor is basically a 5V potentiometer which outputs a voltage from 1-5V depending on throttle pedal position) and then tells the throttle bodies to open appropriately, accelerating the engine/car.

It is possible that a throttle position sensor related to your accelerator pedal is faulty, causing the unwanted acceleration, however I would be surprised as the pedal assembly on these cars incorporates two sensors, wired inverse to one another—the computer then adds these two voltages together (one voltage increases with throttle position, the other decreases with throttle position) and ensures that the voltages add up to 5V. If the combined voltage deviates from
a constant total of 5V, CEL is set and car immediately goes into limp mode. Any sensor deviation related to throttle is a big deal for the computer and the car will let you know right away, not throw a “shadow” code (code present but no warning light) and allow you to continue driving.

I think you need to bring this car to someone who is equipped to diagnose and repair, and if indeed the car accelerates with a mind of its own, I would recommend you stop driving the car and get it towed there. The problem is not going to resolve itself, and will very likely get worse.

 

How many miles, regular service up to date? Sounds like you have 2 faults. RPM increase in taller gears without more accelerator input Sounds like a clutch slipping to me. As far as the CEL code P2073 I would check the air filter boxes for damage (cracked/broken) a small impact will flex in the bumper, damage the box and appear like nothing happened.

 

After taking the car out last night for a diagnostic spin, it does seem like the issue is more likely to be a slipping clutch. Called the local dealer today and got a quote for $15K using Velocity AP clutch kit... Dealer is quoting me 32 hours of labor. Does that sound right to you? Dealer is saying it's substantially more labor hours than the V8 variant. Also, given that the slipping issue just started happing (it only happened twice) any idea how long it can continue before the clutch is completely fired? The car has about 28K miles on the clock.

Thanks all for your help with this.

 

Makes sense, and mileage is about right for needing a clutch.

Who’s the dealer, and do you already have an existing service relationship with them? I would definitely give
them the opportunity to diagnose the car before committing.

I’m sure the flat-rate book time is 32 hours on that job. I can’t imagine anyone billing fewer hours than that. Realistically, it’s a huge job with hundreds of steps that must be performed exactly right requiring tens and hundreds of thousands of dollars of very specialized equipment. The whole car is going to come apart. Sounds like the labor-rate is somewhere in the neighborhood of $300/hr? That is pretty expensive, just make sure that you are getting a quality job.

Unless you have an alternative shop that you can trust to do the work, you’re probably going to have to just pay whatever it costs and be glad you can afford to drive an AM. Don’t get fleeced, but life is short, and if the guy turning the wrench can’t make a decent living, no one gets to drive. It is hard work.

Just make sure that they warranty the job (especially if they are not using AM parts) and provide you with a loaner.

Assuming the clutch is slipping, it’s only going to get worse. Get the car scheduled for the clutch job, but don’t be afraid to drive it while you wait. You could probably nurse it and have the thing last another year, but why? What is the sense in driving a broken V12 sports car that can’t put the power down?