Hi All,

Back again and looking for some advice…

I have a 2013 V8 manual Vantage and am dealing with a recurring error: "P2135 - Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation".

I've found plenty of discussions about cleaning the throttle body, which I did on the original unit. However, the tracks were severely worn. After cleaning (it was a bit gunky), there was no improvement, so I replaced it with a good second-hand part from eBay.

Despite the replacement, the issue persisted. I then swapped out the throttle pedal—again using a good second-hand part from eBay. This initially seemed to improve things, but now I am back to square one—car stuck in limp mode on the driveway.

I've removed and cleaned the replacement (eBay new to me) throttle body, but that hasn’t made any difference. The wiring and connectors at both ends appear to be in good condition, and I don’t see any obvious issues with the air intake etc. and I have no other codes.

Interestingly, if I drive carefully, I can avoid triggering the code. However, the moment I aggressively overtake (e.g., in 2nd gear) or rapidly take off from a standing start, limp mode kicks in, and I’m back to square one.

Before I head down another rabbit hole, I’d appreciate any pointers or suggestions on what to check next.

Thanks in advance,

Lee

 

I'd see if you can back probe the connector on the gas pedal to see what voltages each sensor is showing. They have to be pretty close or it throws the error code. You'll need a wiring diagram to know which pins to check. It may be that the used pedal you got has failed as well.

 

Hi David,

Thanks for coming back to me.

I haven't back probed them yet, bit tricky under the dash, but I have looked at live data on my diagnostics.

At tick over:
Pedal sensor 1: 3.98v
Pedal sensor 2: 0.50v

At full throttle it's the other way.

You're right there is a chance the replacement one has also become faulty. I have a new working throttle body arriving soon. I'll try that and if it's the same I will order up a new pedal.

I managed to capture some live data as it went into limp mode and there is nothing obviously wrong. Voltages on both the pedal and throttle body look fine.

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Hi all,

I wanted to follow up in case anyone comes across this in the future and finds it useful. I’ve been investigating the accelerator pedal sensor voltages on my V8 Vantage using a scan tool, as there is very little documented information in the workshop manual or online regarding expected values.

However, I did find a reference to the DB9 accelerator pedal, which uses the same part as the Vantage. The DB9 manual states:

"APP1 should read 4.0V at idle and 0.5V at full throttle"
"APP2 should read 1.0V at idle and 3.5V at full throttle"

The Vantage accelerator pedal (same as DB9) has three sensors, which my Launch scan tool detects as:

PPP1
PPP2
PPP3

Looking at the wiring diagram from the Vantage workshop manual, I found that:

Switch A (Right Side of pedal) contains two sensors and has six cables.
Switch B (Left Side of pedal) contains one sensor and has three cables.
For Switch A, the two sensors work in a positive-negative pair, meaning their combined voltage should total 4.0V at all times, regardless of throttle position. This is consistent with what I measured on my car.

When checking APP2 on my car, I get:

0.4V at idle
Maximum of 3.19V at wide open throttle (WOT)
According to the DB9 manual, this is too low—it should be 3.5V at WOT.

It’s likely that when I go full throttle, the ECU expects 3.5V but is only seeing 3.19V. The voltage is out of range, causing the ECU to enter limp mode.

Interestingly, I swapped back to my original pedal, and the issue remains identical. This suggests one of two possibilities:

I coincidentally have two faulty accelerator pedals.
The issue is elsewhere in the system.

I’m fairly confident that the wiring and connectors are fine, because:

The voltage readings are stable—there are no spikes or drops.
When I unplugged Sensor 2 (left side of the pedal), I got 0V on diagnostics and multiple error messages on the dash (Traction Control, ABS, etc.), meaning the ECU is detecting sensor disconnection correctly.

I’ve ordered a new throttle body and accelerator pedal, and I’ll update with my findings once they arrive.

If anyone has official voltage specs for the Vantage that differ from the DB9 manual, I’d love to hear them!

Hope this helps someone in the future.

Lee

 

Good info. Presumably the sensors act as some kind of potentiometer and vary resistance. You could try measuring resistance, but without knowing expected values I don't know what it'd tell you.

You could maybe try emailing someone like VAP or Bamford Rose and see if they know what values to look for.

Your scan tool is presumably showing the values seen at the ECU. You'd have to measure at the pedal to verify the same voltages are seen there.

 

Thanks David,

I’ve reached out to Bamford Rose a few times—not specifically for this information, but regarding other parts I was looking to purchase or upgrade. Unfortunately, I’ve never received a response.

Just a quick update—I came across a section in the workshop manual related to the P2135 code, as shown below.

I decided to replace the throttle body with the new one I had ordered, mainly because it arrived before the accelerator pedal. After fitting it, I took the car out for a test drive, and immediately, all my issues were resolved. Throttle response has significantly improved, and there’s no longer any P2135 error code or limp mode. I’ve driven approximately 50–75 miles since the replacement, replicating my usual driving style, and so far, everything remains trouble-free. The car feels noticeably better, which is fantastic news - for me.

The throttle body part number is "6G33-9F991-AA", which I believe is standard across all Vantages. I’ve made some enquiries to see if my faulty unit could be re-engineered or repaired, but I’ve had no success so far. It’s a bit frustrating, as these are Bosch parts, and while similar ones are readily available online, they aren’t compatible. However, I did find a company that can rework the DB9 throttle body.

Hopefully, this information will be useful to someone in the future!

 

Interesting. So presumably the reading from the throttle butterfly position sensor didn't match what the ECU expected. The used part had the same issue as your original. Could try taking apart the throttle body to see if you can tell what is the issue for posterity since it's junk anyways. How much was a brand new throttle body?

 

I too have never received a response from Bamford Rose. If anyone has cracked that nut....

 

Exactly that David. Either the voltages on the A/B side didn’t correlate, or there was a significant enough time delay to trigger the ECU warning. Cabling was another possibility—I’ve read that some owners have experienced issues and had to replace the wiring harness.

This past weekend, I was already planning to swap out all my brake callipers (plus new front discs) for a refurbished and freshly painted set. While the car was up on stands, I removed the passenger-side liner (UK) and inspected the wiring harnesses and plugs connected to the ECU. I didn’t go too deep into the inspection, but everything appeared as expected—nothing stood out.

The first throttle body (the one on the car when I bought it) was definitely worn, with the tracks almost entirely gone. The second one looked fine, even on the bench. If I get the time, I might check the output voltages to see if I can pinpoint the issue—something for a rainy day. A new throttle body costs around £750 (including VAT) on astonmartinbits.com. There are quite a few second-hand options available, but, as with anything used, it’s a bit of a gamble.

@Marmot It’s a shame—I wanted to give them some business since Mike’s videos have been a great help. They were one of the reasons I decided to buy a V8V.

 

Yes, I've emailed them a number of times to inquire about the glass switch kits that they sell and have never hard a thing back but noticed the pricing had changed, so I assume they are still able to make them. Shame because I have a set of the factory ones but I'm missing the bespoke portion so the car would be weirdly mismatched.

I have always like his videos, particularly the weapon of mass petrol consumption....