Not the throttle pot issue again :)

Ian H

Junior Member
Messages
120
I had put the 3200 away for 3 months while rebuilding a triumph spitfire with/for my son.
It is now having a major sulk and has zero throttle reponse on start up. It has always been grumpy, throwing increasingly frequent CIL warnings, but now nothing .
I went to check the potentiometer output but cannot detect the 5v input from the connector plug into the unit.
Tried meauring car earth to 5v input pin and also earth pin to input pin but nothing.
Does anyone know which fuses/breaker this is fed by ? Maybe the problem is at the supply end?
Is there an affordable solution for this - I know there was a forum solution at one stage- or is it £540 to Europsares for a new one which I think is unavailable anyway?

With regards to the related error codes I am getting:

PO120 Throttle Position Sensor/Switch A circuit malfunction
PO220 Throttle/Petal Position/Sensor Switch B circuit malfunction
PO221 Throttle/Petal Position/Sensor Switch B circuit range /performance problem

Many thanks as always
Ian
 
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NickP

Centenary Club
Messages
1,539
Get a contactless throttle pot from I think it was Davy on here? They are also on ebay here https://www.ebay.co.uk/itm/284420143523?hash=item4238c2f9a3:g:BlAAAOSwEkhZwAng

You can do a throttle pot reset which involves turning on the ignition with the pedal fully depressed for 30 secs - then off - then on again with no pedal for 30 secs, this sometimes at least gets you home etc. (I may have this procedure the wrong way round but a search on here should help you)
 

Ian H

Junior Member
Messages
120
yep that's a whole lot cheaper .. but if I am not gettting any power to it then I guess this one won't work either?
 

davy83

Member
Messages
2,495
Hi. I still make contactless replacement pedal sensors and you can buy direct from me rather than go through e-bay (more expensive) or try my new on line shop at www.maserati3200.net.
However if there is no 5V supply to the pedal sensor then a replacement won't fix this. Can you take your meter and measure the voltage on all 6 wires on the pedal sensor with the ignition on? and tell me what the readings are. Its often easier to clip the 0v lead on your meter to the bodywork so give you a free hand, and make sure your meter probes are thin enough to get into the connector pins so you know you are making contact. 2 of the wires should have a 5V DC power supply on them. Also measure ohms to the car body on all 6 wires with the ignition off. Two of the wires should have low ohms like 1 or 2 to car body.

This diagram shows the 4 wires my new sensor uses but this will indicate which ones roughly you need to look at.
90427
I am pretty sure the 5V supply for the pedal sensor comes from the ECU. So if its dead then this would be a pretty serious problem. you need to confirm
 

Ian H

Junior Member
Messages
120
Hi
I will double check the voltage and resistance figures tomorrow and let you know.
As you say it is tricky to get a good connection on the small connector pins.
presumably I need to take the readings from the back of the plugs with them still connected?
Many thanks
Ian
 

NickP

Centenary Club
Messages
1,539
I am good mate. There’s an Ace early Oct, you coming along?
If I can get it back on the road by then then I may come along, just been fitting a new water pump, radiator, cam belt etc and tidying up the engine bay, been off the road all year pretty much :-(
 

conaero

Forum Owner
Messages
32,327
Sure, if you’re changing the cambelt make sure you change all the idlers, seen the casting shear and take the belt off obvs.
 

Ian H

Junior Member
Messages
120
Hi
Ok so I have checked the resistance and voltage properly. I have:
4.9V input
0.39V rising to 3.05V for Out 1
0.39V rising to 3.02V for Out 2
and less than 0.1 ohm reistance on the two ground terminals

Based on this I think everything should work ok?

Tried the throttle reset a couple of time but still zero throttle response?

Hmmm Italian wiring, don't you just love it :(
 

Oneball

Member
Messages
7,083
Have you checked for power at the throttle body? When you turn the key on the throttle body should open and close as a check.
 

Ian H

Junior Member
Messages
120
Ok so after multiple throttle resets outputs have nwo settled to:
0.39 rising to 3.08/3.09 at full throttle
0.39 rising to 3.04/3.05 at full throttle
The max value range is due to my multi meter having 10 mV accuracy when reading above 2V.

So max. values have crept up by ~20 to 30mV but difference between the max readings is still of the order of 30-40mv.
It seems from prior threads the max. differential is ~20mV so I guess this could still be the issue. Seems crazy sensitive to very small differntials in voltage?
 

Ian H

Junior Member
Messages
120
ok so gets weirder.
Took inlet air hoses off and manually pushed throttle butterfly open and closed a few times - now runs perfectly.
Well at least for 5 minutes:)
Have one of Mike Robert's after market throttle bodies
 
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davy83

Member
Messages
2,495
Ok so after multiple throttle resets outputs have nwo settled to:
0.39 rising to 3.08/3.09 at full throttle
0.39 rising to 3.04/3.05 at full throttle
The max value range is due to my multi meter having 10 mV accuracy when reading above 2V.

So max. values have crept up by ~20 to 30mV but difference between the max readings is still of the order of 30-40mv.
It seems from prior threads the max. differential is ~20mV so I guess this could still be the issue. Seems crazy sensitive to very small differntials in voltage?
your readings are good. The ECU is not as fussy about the difference away from idle (I reckon above 0.7v), so the difference at higher pedal positions will be fine. Yes Maserati clearly screwed this up, and set a 15mV difference limit on the idle voltages which is a positional error of 0.23 degrees of rotary movement between the two sensors. It is near impossible to get a rotary sensor to be this accurate, and probably why Bosch won't make them any more.
I think the Maserati thinking was that they wanted to prevent the engine opening up under fault conditions. if the two redundant sensors are different then one of them must be faulty so you need to go into a fault mode to protect the car. The problem is working out what constitutes a fault. They just guessed wrong, and set it far too tight so they throw errors at the drop of a hat. Unless its one of my sensors of course :)
 

Ian H

Junior Member
Messages
120
Many thanks everyone.
It seems a good dose of throttle cleaner around the butterfly is in order to ensure it doesn't stick during initiation and throw a throttle error.
But I am sure I will be back for one of those shiny new throttle potentiometers in due course :)
 

davy83

Member
Messages
2,495
As long as its working and problem is solved that's a result! Hopefully it will run for a while now so you can enjoy it.