Throttle Angle readings

Whether it is with the Sykes Pickavant ACR or Multiecuscan, I remember being able to read throttle angles without the engine running. Doesn't seem to be the case anymore. Anyone knows why that is the case?

Presumably you have the ignition on and have established a connection with the ECU, and can get other parameters like air and coolant temps, etc.? I think you get TPS voltage as well as opening degrees? Maybe the TPS is faulty..but I'm sure you would have noticed that?

Yes, ignition on and connection all established...just that opening degrees won’t be shown until engine is fired up. TPS is working as it should I suppose? Or else it wouldn’t be showing readings (with engine running) and driving as normal.

Anyone? What are you guys experiencing with your code readers?

Yes, you should be able to get throttle position degrees and voltage readings with ignition on without starting engine, on the ACR4.

Thanks for confirming that Graham. I don’t seem to be able to do that anymore... any idea on why that is the case?

What readings exactly is it giving for voltage/angle with engine off, even if they don't change with pedal movement?

If it's giving good readings with engine started I wouldn't be too worried, maybe dodgy TPS or wiring?

Off-hand I can’t remember what the readings are with engine off but I remember it being normal. I don’t have any running issues. Just that it’s very difficult to see what the WOT readings are with engine running and revving the nuts off it. I’ve tried other TPS as well so unlikely to be that. Also tried measuring another car and it’s also doing the same thing of not giving readings unless the engine is running.

I just tried on my Porto 20vt and can get voltage and angle readings on the ACR4 with just ignition on, but engine not running. Although at WOT it was only reading 62° (and 4.4V) whereas I thought WOT was something like 84° The cars in bits at the moment so don't want to start it in case there's something missing (no brakes at the moment for example). I'll try on the Plus if I get a chance.

Just tried mine and got exactly the same readings as DaveG above and I can't currently start engine either.

Suspect it's just a "feature" of the ECU.

When I fitted a new TPS years ago I was definitely able to test to >85 degrees with engine off and adjusted throttle cable/pedal accordingly. The ECU manual isn't exactly that clear on which TPS parameters are available with only ignition on and which need engine running, but it does show that to read *all* the TPS parameters the engine has to be running and only one seems to be available with engine off.

The ECU handles Absolute angle , Relative angle (Absolute Angle - minimum threshold) and voltage on potentiometer, whereas the ACR4 only shows angle and voltage so it's not showing everything anyway. It doesn't say how the "minimum threshold" is calculated but maybe that has something to do with it and the difference with engine on/off. Looks like it may be only capable of giving the absolute angle with engine off and absolute and relative with engine running.

Similarly, years ago I adjusted my WOT angles exclusively with the engine off through the the ACR. Themaximum was able to see it to was about 82 or 83 degrees. Never been able to go beyond that.

I can’t work out what changes I did since then which would alter this capability. I’ve never replaced my ECU (only the chip). The TPS was the same one as well.

Multiecuscan also did not allow me to see it with just ignition on.

Got to the bottom of this for my coupe anyway... it was because the battery had been disconnected and engine not started before checking the readings.

Probably the "minimum threshold" value that's used by the ECU to calculate the relative throttle angle is lost when power is disconnected and only re-calculated when the engine is running.

Previously max throttle reading was 62 degrees, but with engine started and rev'd slightly then switched off it was showing 82 degrees at full open throttle.

That would make an amount of sense. I recall that the widget would sometimes return the throttle without the engine running, and sometimes not... never investigated sufficiently to get to this level of detail, but the 20v throttle position is differential while the 16v throttle position is absolute.

Neil

Great find guys. That seems logical. However, I've not disconnected my battery for quite some.
Based on your description Graham, it doesn't seem like the ECU would take long to recalculate its values?

Yes, just one start.

Try the same series of actions I did :

1) Disconnect battery for a minute then re-connect
2) Connect ACR4 to diagnostic socket and battery
3) Switch on ignition and start engine
4) Make ACR4 connection to ECU
5) View "components" display, confirm throttle position value responding to pedal and throttle status value can show "idle" and "mid"
6) Switch off engine
7) Disconnect and re-connect cable from ACR4 end to reset it
8) Switch ignition back on but don't start engine
9) Make ACR4 connection to ECU
10) View "components" display, floor throttle pedal and confirm throttle position showing up to 82 degrees

Steps 7 and 8 may have been switched around, so try both ways if one doesn't work for you.

Graham, I’ve followed your series of action diligently but the TPS angle remains unresponsive at ignition only.

TPS voltage was responsive though..

What range or number did it actually show on the ACR4 for throttle angle when moving the pedal?

Throttle voltage started at 0.3v... the angle was 0 and stayed 0...or did you mean with the engine running? With engine running, I think I saw it go to 83 degrees with a quick jab on the throttle.

OK, it's not doing the same as mine was then, I was getting a proper reading that changed but just not over the correct range.