V8 Vantage - P2135 Error
Discussion
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
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
Hi Scubalee,
I can offer you a theoretical explanation of P2135 via a narrative without specifics with your MY car.
With a P2135, the operative in the description is "A/B voltage correlation"
With drive by wire schemes, basically, a variable voltage signal is sent to a receiver which operates a step motor to accomplish varying motions of the throttle body butterfly valve.
Think of the throttle pedal as a variable resistor that sends voltage signals to the receiver on the TB. Let's use a voltage range of 1v to 5v to accomplish a full motion range of the butterfly from idle to full throttle. so:
1v would = idle
5v would =FT
Think from an idle, when you launch and as you accelerate, commanding full throttle, the pedal sensor starts with 1v then operates through an ever increasing voltage to 5v to get to full acceleration by commanding the receiver step motor to open more and more to fully open.
Now comes the P2135. Somewhere within that voltage range (1v to 5v) a dropout is occurring (and in your case, appears to be intermittent). A dropout is when, for a moment, the voltage drops to 0v. The ECU cannot process that 0 voltage as it has no correlation in its expected field of operation. The ECU responds with an immediate CEL and a limp position. Limp is especially important with a drive by wire because, if it didn't the car could become uncontrollable at some acceleration (driver control lost).
Finally now, back to your specific situation. A P2135 is almost always a bad pedal sensor (voltage sending unit), and it could also be the receiving unit (on the TB). You said you purchased used parts (of both the sending and the receiving units) from Ebay. Personally, I wouldn't shop an electrical part used. It's kind of like buying used spark plugs. If I had a P2135 I would want a brand new sensor, then a brand new receiver if one or the other did not solve the problem.
On a P2135, there is a possible third fault - the ECU is bad. But, from what you're describing (the intermittent part) I would be focusing on these two parts first. A distant fourth possibility is the harness that goes from the pedal to the TB has a pinched signal wire that might only be shorting when you are hard accelerating but during more moderate starts doesn't disrupt the signal.
Hope this helps and apologize for the windy explanation.
I can offer you a theoretical explanation of P2135 via a narrative without specifics with your MY car.
With a P2135, the operative in the description is "A/B voltage correlation"
With drive by wire schemes, basically, a variable voltage signal is sent to a receiver which operates a step motor to accomplish varying motions of the throttle body butterfly valve.
Think of the throttle pedal as a variable resistor that sends voltage signals to the receiver on the TB. Let's use a voltage range of 1v to 5v to accomplish a full motion range of the butterfly from idle to full throttle. so:
1v would = idle
5v would =FT
Think from an idle, when you launch and as you accelerate, commanding full throttle, the pedal sensor starts with 1v then operates through an ever increasing voltage to 5v to get to full acceleration by commanding the receiver step motor to open more and more to fully open.
Now comes the P2135. Somewhere within that voltage range (1v to 5v) a dropout is occurring (and in your case, appears to be intermittent). A dropout is when, for a moment, the voltage drops to 0v. The ECU cannot process that 0 voltage as it has no correlation in its expected field of operation. The ECU responds with an immediate CEL and a limp position. Limp is especially important with a drive by wire because, if it didn't the car could become uncontrollable at some acceleration (driver control lost).
Finally now, back to your specific situation. A P2135 is almost always a bad pedal sensor (voltage sending unit), and it could also be the receiving unit (on the TB). You said you purchased used parts (of both the sending and the receiving units) from Ebay. Personally, I wouldn't shop an electrical part used. It's kind of like buying used spark plugs. If I had a P2135 I would want a brand new sensor, then a brand new receiver if one or the other did not solve the problem.
On a P2135, there is a possible third fault - the ECU is bad. But, from what you're describing (the intermittent part) I would be focusing on these two parts first. A distant fourth possibility is the harness that goes from the pedal to the TB has a pinched signal wire that might only be shorting when you are hard accelerating but during more moderate starts doesn't disrupt the signal.
Hope this helps and apologize for the windy explanation.
Hi Skhannes,
First of all, thank you for your response. That was a fantastic explanation, and I really appreciate you taking the time to reply. Everything you've said is absolutely spot on.
This morning, I managed to secure another throttle body (one that is known to be working), so I’ll give that a try before committing to a new one. I also completely agree with your point about new vs. used parts, and I’ll go down that route if necessary. I’m also planning—though I haven’t done it yet—to set up my Launch scan tool to record both the pedal and throttle body voltages while driving. I’ve already checked them at idle, and they appear consistent, which makes sense.
My gut feeling aligns with yours—one of the used parts is likely faulty, and I’m hoping I can catch it on "record" when it fails. Last year, I had to remove the air intake manifold to replace the secondary air pump, so there’s a possibility that I accidentally damaged a cable. That said, I’ve done several thousand miles since then without any real issues, though that doesn’t necessarily mean it isn’t the cause.
Thanks again for your insights—I really appreciate it!
First of all, thank you for your response. That was a fantastic explanation, and I really appreciate you taking the time to reply. Everything you've said is absolutely spot on.
This morning, I managed to secure another throttle body (one that is known to be working), so I’ll give that a try before committing to a new one. I also completely agree with your point about new vs. used parts, and I’ll go down that route if necessary. I’m also planning—though I haven’t done it yet—to set up my Launch scan tool to record both the pedal and throttle body voltages while driving. I’ve already checked them at idle, and they appear consistent, which makes sense.
My gut feeling aligns with yours—one of the used parts is likely faulty, and I’m hoping I can catch it on "record" when it fails. Last year, I had to remove the air intake manifold to replace the secondary air pump, so there’s a possibility that I accidentally damaged a cable. That said, I’ve done several thousand miles since then without any real issues, though that doesn’t necessarily mean it isn’t the cause.
Thanks again for your insights—I really appreciate it!
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
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
I had a similar problem with by 2006 V8 Vantage. It occurred a few times just after I bought it from McGurks.
Tried a new throttle body (no difference), took the throttle pedal off and cleaned the carbon track (no difference). In the end it went to a local AM "specialist" who couldn't find anything wrong, cleared the error and charged me £400 for the privilege.
Guess what, it went again.
In the end it was trailered back to McGurks and they eventually diagnosed an intermittent wiring problem. They had a new section of the harness put in between the throttle pedal and the throttle body. That cured it. Strangely, within a month of this they had another V8 Vantage in with exactly the same problem.
Same cure.
So if you can't solve this I can recommend McGurks as they have a technician who has "seen it all before". Car has been back with me for more than 18 months and no repetition of the problem.
It was very frustrating and would only go into limp mode at the further point from home! If you ring McGurks ask for Matt as he knows of the problem. I could have taken an axe to the car!
Tried a new throttle body (no difference), took the throttle pedal off and cleaned the carbon track (no difference). In the end it went to a local AM "specialist" who couldn't find anything wrong, cleared the error and charged me £400 for the privilege.
Guess what, it went again.
In the end it was trailered back to McGurks and they eventually diagnosed an intermittent wiring problem. They had a new section of the harness put in between the throttle pedal and the throttle body. That cured it. Strangely, within a month of this they had another V8 Vantage in with exactly the same problem.
Same cure.
So if you can't solve this I can recommend McGurks as they have a technician who has "seen it all before". Car has been back with me for more than 18 months and no repetition of the problem.
It was very frustrating and would only go into limp mode at the further point from home! If you ring McGurks ask for Matt as he knows of the problem. I could have taken an axe to the car!
Thank you both - much appreciated.
Just a quick update — I came across a section in the workshop manual related to the P2135 code.
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!
Just a quick update — I came across a section in the workshop manual related to the P2135 code.
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!
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