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I've had L and R check engine lights for a while [91 diablo]

Both sides flash 12 times, I understand this to point to the throttle potentiometer.

I bought a new one, put it in. Checked the connection was good, checked that there was voltage [5v] on the connector to it.

I disconnected the battery to clear the errors.

When I restarted the car the chk eng lights both came back on and stayed on, and 12 flashes indicates the same problem.


Are there any boffins out there with an idea of what to do next. How critical is the alignment of the sensor ?

Thanks
 

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Mike adjusting the TPS is not all that easy. I have written up something at

http://www.lamboweb.com/Repairs_Section/Repairs_Throttle_Position_Sensor.htm

which gives you an outline. It may not be adjusted correctly. Also you cannot reset the computer by switching off the battery. The LIE computer stores error codes for years (actually 50+ start/stop cycles at least). You need to have a dealer do it (they have a computer setup to read and clear errores etc.) or carefully do it yourself as described in

http://www.lamboweb.com/Repairs_Section/Repairs_Reset_LIE_Computer.htm

Be real careful with the connections. On later cars it is easy because they have a OBDII connection!
 

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Discussion Starter #4
Thanks guys.

Reassured to hear that the setting is critical, at least gives me something to work at. Will look again tomorrow.

After I disconnected the battery, there were no error codes on flashing on and off the ignition. The error codes only reappeared after the car was started.

I thought long and hard about restting the computers by making a jumper across the socket as described on Lamboweb. I chickened out for fear of damaging one of the ECUs, although if it works this is an easy way of resetting the computers.

JRV, the action of the potentiometer appears smooth, where does the slight click come from ?
 

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Discussion Starter #5
BTW, disconnecting the battery means jacking up the car and unbolting the terminals from it, not using the 'kill switch'.
 

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Discussion Starter #6
OK, so have checked the setting with digital multimeter. Get about 4 ohms across a to b, as described on John's excellent article. [it was 35 ohms where I had it !]

I reset the computers by junmping across pins 7, 9 and 13 on the diagnosis socket [brave], and then when it starts the check engine lights return, both banks 12 flashes.

I notice that when the TPS is full throttle, the resistance is only about 400ohm - anyone any ideas ???
 

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Do you have the service Manuel for the early cars?

You may need to do a value test, using the specs in the book, to check for bad wires/connections/ground circuit.

Howis throttle response with the new TPS compared with the old one and also how do the ohm compare with each other?
 

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Discussion Starter #8
Thanks for the response, JRV

The manual I have is from Jan 1993, so a bit later and a few obvious differences, especially electrics. The manual suggests to "check wiring connection as indicated on diagnosis procedure", whatever that means.

I would like any insight into how and where to check the circuit / bad grounds etc, I am well used to checking the integrity of wiring [i'm a boater], but need some insight as to where to look.

Throttle response seems about the same with new and old tps sensors.

I checked with my [marine based] meter, the old sensor reads a minimum of about 40 ohm, the new sensor does appear to read about zero ohm to about 600. I was able to make it read 3.7 ohm installed in the car
 

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Discussion Starter #9
Still not been able to resolve it. Have reset computers several times, check engine lights L+R appear every time. I have noticed that by moving the TPS with the engine running, there is a slight [temporary] effect on revs.

I think it might still be an adjustment problem.

Can anyone else confirm the resistance that should be across the TPS when the throttles are closed.

I'm pissed that my car came back from an authorised Lambo service centre with this known problem, despite written instructions in two languages

Happy new year to all.
 

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Maybe I can help, maybe not.
My 91 had the same issue, I purchased a new tp and tried to set it according to the same website as you and had no luck. This is what I did. (this is how we set up our v8 hot rod cars!) Using a fluke digital meter I grounded the negative side of the meter to the block then I put the positive probe of the meter into the rear of the center terminal of the tp connector with it still connected to the tp. set the volt meter to dc volts. turn on the ignition of the car but do not start it, make sure your battery is charged fully. What you are looking for is approximately .8 volts, adjust the sensor until you have .8, You should be able to adjust it anywhere from .5 to .9 and it will work. The closer you get to .9 the leaner the mixture should theoretically become. This is a 5 volt system just like a gm. You have 5 volts coming in, a ground wire and a signal wire (the center terminal) You are checking the signal wire for approx 1/2 volt (.5) at idle, mine seems to work best at .8 volts. after you have set it roll the throttle wide open (engine off, igntion on) and you should have close to 5 volts (mine read s 4.8 volts). In order to do this you do have to pull the rubber boot back that is on the connector, and reconnect it to the tp. Make sure you reset the computer again. When you reset the computer connect the three terminals together, turn on the ignition and wait until the check engine lights go out. Then turn off the ignition and pull you wires out of the diagnostic port. If you do not do it this way it will not reset the computer. I hope this helps. It worked for me!
dave
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:cool:
 
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