Erratic Tps 34 Gtr

[paulr33]

-0.36mv - where are you seeing that?

the hand controller ,reads straight from the ECU, which is coming from the TPS wire from the engine bay

from there, the PFC sends the TPS signal on another wire, to the ABS/A-LSD computer in the boot

so its that wire you need to check if its the same voltage (it sohuld be)

if TPS on the hand controller is always OK this means the sensor is OK and the wire from the sensor to the main ECU loom is OK

from there the PFC (and stock ecu) relay this signal to the ABS/A-LSD computers in the boot as the A-lSD needs to know how hard you pull the throttle cable

if that TPS signal *(the one relayed to the boot PC) dies, out of range or goes spazzo the A-LSD computer goes into fail safe mode and the light comes on and the A-LSD system gives up, ie no lock when wheel spin

[rob82]

been testing the voltage at the fc. with just the ignition on the volts to the fc are 0.568, it matches the hand controller voltage. Also the output to the attessa reads the same.

Once ive started the car the voltage at the fc slowly drops to -0.36mv, as if its lost the signal but the hand controller still states it has 0.5v. now im confused. is this a correct reading for tps output or is this why my

fault light is coming on?, but the hand controller says its all good. ahhhhhhhhhhhhhh

First check your battery and ground terminals are tight. Then:

Mesure your 5V rail vs sensor gnd with ignition on and then with the car running and see if it changes. Then measure your sensor GND to chassis gnd and see if there is any voltage difference between running and ignition on.

Also try disconnecting the TPS with the car running and also with ignition on to make sure it drops to zero so you can see that the hand controller isn't just giving you false information.

Has anybody ever checked the input impeadance of the TPS signal into the PFC and the attessa system matches??

[trick]

i got the negative mv reading from the tps wire at the fc (#38) but only once the car is running. when the ignition is only on its fine at 0.568 v.

once i start the car the #38 wire starts at a low 100mv and slowly drops to the negative mv, can range up to -138mv then the fault light comes on. this does not happen all the time if the mv signal stays around -0.70 consistantly or under -0.7mv, the fault light does not come on but if it spikes lower it faults. but sometimes it stays at 100mv and no fault light.

could this be an earthing problem with the fc? engine or tps?

Rob82 which is the 5v rail i should test to gnd? ill test all the grounds and see if i get and changes or differances

[trick]

Pulled out vin tps once running. Fault came up and tps signal went to 0.00 and black background on the sensor. Checked tps signal wire to tps earth read 0.5v. Then checked tps signal wire to chassis earth it came up with the negative mv reading. So checking figures to chassis earth gives me the negative reading. Still once the voltage reading spikes negative the fault comes on.

[rob82]

Pulled out vin tps once running. Fault came up and tps signal went to 0.00 and black background on the sensor. Checked tps signal wire to tps earth read 0.5v. Then checked tps signal wire to chassis earth it came up with the negative mv reading. So checking figures to chassis earth gives me the negative reading. Still once the voltage reading spikes negative the fault comes on.

There is three pins at your tps 5V, signal and sensor GND. Check that the voltage between 5v pin and the sensor gnd stays @ 5V all the time - if it doesn't your have to start there - thats a big problem. You should always check sensor voltage with reference to sensor gnd not chassis gnd.

That being aid if you have negative dc voltages between signal and chassis earth you may have a rectifier issues within you alternator. you could try disconnecting the battery cable to the alternator with the engine running and see if the erratic tps goes away.

[trick]

There is three pins at your tps 5V, signal and sensor GND. Check that the voltage between 5v pin and the sensor gnd stays @ 5V all the time - if it doesn't your have to start there - thats a big problem. You should always check sensor voltage with reference to sensor gnd not chassis gnd.

That being aid if you have negative dc voltages between signal and chassis earth you may have a rectifier issues within you alternator. you could try disconnecting the battery cable to the alternator with the engine running and see if the erratic tps goes away.

ah i see, yeah the tps remains the same 5v, but only when i test it with the tps earth. if i test the 5v with the chassis ground is where the problem lies. thats when i get the negative mv.

from what ive found 9correct me if im wrong, is that the signal for the handcontroller uses the tps earth giving it 5v. when i test the signal wire #56 which the fc use to translate the tps signal to the attesa it uses the chassis earth which is in mv. my erratic mv signal dropping to the negative trips the fualt.

SO

i put another earth from pin #60 (fc main gnd) to the chassis, where the fc bolts onto the chassis including the fc bracket. What this did is stop my negative mv reading and brought it up to 300mv around there but not in the negative. This in any way has not affected the 5v reading to the tps or hand controlled its simply having a better ground to the fc

so far i have not had the fault come on, YET!!!!

so far so good.

keeping the signal to the attesa in the posative mv range seems to have fxed it, but i havnt got my hopes up

thanks to all who have spent the time to post on this thread.

ill post back here if it fails again

[Keeper]

Sorry to thread-jack. I'm having issues with my ATTESSA and TPS and reading through this I think I might be going down the right track now...

I am having my 4WD light com on and throw a TPS error code at me intermittently from 1-10 minutes of driving, usually at lower RPM. I have just swapped battery and alternator, the Power FC is reading 13.4V at idle now, and a tad under 12 with IGN OFF. My battery has been reloacted to the boot, using some heavy duty wiring.

I checked the voltages and resistance today on my TPS;

- I'm getting a good 5V constantly from +5V TPS Ground

- Signal -> TPS Ground or Engine (Plenum) it shows 0.5 Volts, as shows on the Power FC controller, and as does when tested from the ECCS module between 30 & 38pins.

- When I checked the same Signal wire to Car Chassis it is showing a higher 0.7V.

- I measured resistance from chassis to block and it reads 0 Ohms then Started the engine.

- The TPS now reads 0.53Volts Singal to TPS Ground, 0.66Volts Signal to Engine, 0.5mV or -0.5mV Signal to Chassis

Would I probably be correct in assuming I have an earth problem, especially as the TPS appears to test fine in almost every way the manual lists.

ADDITIONALLY

Running ATTESSA Fault Code 21 Tests showed me I should recieve approx 0.375V between 50 and 38, but I am getting 0.5V between the two, so the voltage is NOT stepping down to the ATTESSA output.

Thanks in advance to anyone who can help me with this, I'm going nuts

[paulr33]

if TPS is 0.53v at idle this poses no issue for the ATTESSA system or the stock ecu

its only when its 0 that the ECU will throw on the engine check light or the ATTESSA system would crack the sads - much like the A-LSD system does

[rob82]

if TPS is 0.53v at idle this poses no issue for the ATTESSA system or the stock ecu

its only when its 0 that the ECU will throw on the engine check light or the ATTESSA system would crack the sads - much like the A-LSD system does

I doubt it would be 0V - most ECU's will recognise an upper and lower voltage input an it is rarely 0 or 5V more like 0.3V and 4.7V.

And yes it does sound like an earth issue - try tying your grounds together like the original poster and see what happens.

[Keeper]

I doubt it would be 0V - most ECU's will recognise an upper and lower voltage input an it is rarely 0 or 5V more like 0.3V and 4.7V.

And yes it does sound like an earth issue - try tying your grounds together like the original poster and see what happens.

Thanks for the replies guys, I will re-earth the whole car tonight, might look at running another earth cable from block to chassis as well, weird I had put 100km on the engine before this started to happen, would have though it would have shown up form when the fresh engine went in right away.

[Keeper]

Hi guys,

Does anyone have an idea what is an acceptable amount of resistance for the ECU (ECCS) earth to chassis, or where the ECU actually earths to the chassis via.

Thanks

[trick]

hey it does sound like a simular issue i had.

if your getting a erratic negative voltage from the tps at the fc when earthing to chassis then run a temporary new earth from pin #60 (fc gnd) to the chassis (like where the fc bolts up) and then re test the signal from the tps to the fc ( pin #38)and see if it clears up the weak signal. your correct you should read over 300mv as the attesa uses that signal.

to answer your question im not sure on the resistance but it should be minimal.

[Keeper]

Thanks, will give that a go tomorrow, I re-earthed the chassis to engine tonight, better in every way, except the same 4WD fault so will try the extra earth technique tomorrow night. I'm assuming you don't need a think wire, same guage as the ECU wiring should be fine?

[trick]

yeah same gauge wire is fine. also does your car still have the turbo shield earth strap, that does help too.

[Keeper]

No idea where that strap went. Thanks for all the help guys 4WD is running great now, run a wire from pin 60 to the wall and she's a treat. I appear to have some voltage issues still in regards to the TPS though, the 4WD is fine, but I'm having surging idle and poor accel below 3000 rpm. Is it safe to earth the singal ground wire on the ECU to the chassis also?

[rob82]

No idea where that strap went. Thanks for all the help guys 4WD is running great now, run a wire from pin 60 to the wall and she's a treat. I appear to have some voltage issues still in regards to the TPS though, the 4WD is fine, but I'm having surging idle and poor accel below 3000 rpm. Is it safe to earth the singal ground wire on the ECU to the chassis also?

No Definately not. Sensor gnd is not chassis gnd. Have you tryed tying the sensor gnd of both ECU and 4WD together?

[Keeper]

No I haven't the only ground touched so far was pin 60 and the engine-chassis earth where it meets the chassis, should I run a wire from pin 30 Sensor Ground (TPS, Engine temp) back to the ATTESSA computer and joining those two?

[Keeper]

Weird question here; could the earthing of the ECU have changed the CAS sensor return to the ECCS and therefore change my timing?

[rob82]

Weird question here; could the earthing of the ECU have changed the CAS sensor return to the ECCS and therefore change my timing?

If your chassis earthing the sensor gnd - then you will be loading the TPS, ECT, IAT, MAF and CAS. All sorts of bad things will be happening. You should tie the sensor ground of the ecu to the sensor gnd of the ATTESSA. You can also try re earthing all GND wires at ecu and attessa ecu.

[trick]

yeah only earth the pin 60 to gnd (chassis)the tps and ecu use the sensor gnd. earthing the pin #60 should have no effect on the idle, tps or cas.

can always sus out the earth by taking it off again and see if the idle comes good and it goes back to before.