2G NO TACH SIGNAL 2G

[lololobster]

Just thinking out loud here for ideas what I would do as this seems to be a real stickler problem. If possible, after verifying that the signal on pin 4 exists (without any load wires connected to it which may cause it to disappear, although this may be impractical to do), perhaps: disconnect the battery, unplug the PTU, and touch +12v through a small 50-100 ohm resistor in series (to limit current for safety should there be a short somewhere) onto PTU pin 4 of the connector side harness. Measure voltage there and then go around to all the places pin 4 is supposed to go (ECU pin 58, cluster C-05 pin 24, PTU B-62 pin 46 {do this even though the PTU is unplugged}) and see if the same voltage is at all those places. A partial short will show less voltage. An open or bad connection will show no voltage .

Another thing you might try with the battery connected and key to On (so cluster has power) is repeatedly touch (on, off, on, off, etc) that +12v through a resistor to unplugged PTU harness pin 4 to see if the tach gauge twitches. If not perhaps try repeatedly touching (on, off, on, off, etc) a ground to that pin to see if the tach gauge twitches. Of course if the tach gauge expects an entire train of pulses that may not work either - but ya never know, you might get a needle glitch. Perhaps try it on cluster C-05 pin 24 first.

so trying this^ out is probably next on the list but i cant get a resistor until tomorrow, as for anything i can do today, pin 4 runs to multiple places i believe i have already checked ecu pin 58 and pin 24 on cluster connector c-05 but steve mentioned a place on the tcu which i have plugged back in, could there be anything in that area i couldve missed that you know of?

also are there any potential cluster tests i could do that you know of?

 

[luv2rallye]

The places PTU pin 4 (white wire, connector A-92) goes are:
(a) ECU (white wire, connector B-55 pin 58),
(b) cluster tacho gauge (white wire, connector C-05 pin 24),
(c) TCU (white wire, connector B-62 pin 46)

Note: Wire diagrams (aka schmatics) show logical connections (what connects to what regardless of order), NOT physical connections (the actual order in how they are connected) - so don't get misled when you look at them. When a connection shows it's going to 3 places, you don't know the order.

Have you tryed testing the cluster tacho gauge (white wire, connector C-05 pin 24) with your voltmeter freq setting while engine running? If no signal when plugged in, do you see it there with it unplugged?

 

[lololobster]

The places PTU pin 4 (white wire, connector A-92) goes are:
(a) ECU (white wire, connector B-55 pin 58),
(b) cluster tacho gauge (white wire, connector C-05 pin 24),
(c) TCU (white wire, connector B-62 pin 46)

Note: Wire diagrams (aka schmatics) show logical connections (what connects to what regardless of order), NOT physical connections (the actual order in how they are connected) - so don't get misled when you look at them. When a connection shows it's going to 3 places, you don't know the order.

Have you tryed testing the cluster tacho gauge (white wire, connector C-05 pin 24) with your voltmeter freq setting while engine running? If no signal when plugged in, do you see it there with it unplugged?

yea 1 ohm on pin 46, maybe i have 2 bad clusters

also that frequency test ruled out the resistor tap test correct?

 

[luv2rallye]

I assume your 1 ohm is on TCU B-62 pin 46. Are you testing with everything off? Ya that then sounds pretty low but since you switched to a MT you should probably leave the TCU disconnected anyway. Or do you mean it's 1 ohm on the TCU connector (harness side) when it's disconnected from the TCU? That would be a problem. If so, unplug the tacho cluster and the PTU and see if you still read 1 ohm there.

 

[lololobster]

I assume your 1 ohm is on TCU B-62 pin 46. Ya that sounds pretty low but since you switched to a MT you should probably leave the TCU disconnected anyway. Or do you mean it's 1 ohm on the TCU connector (harness side) when it's disconnected from the TCU? That would be a problem. If so, unplug the tacho cluster and the PTU and see if you still read 1 ohm there.

the latter. the tcu was disconnected and i ran from tcu harness b-62 pin 46 to backprobed pin 4 PTU connector with ptu plugged in(probably shouldve unplugged ptu)

edit with ptu unplugged it was .4 and the cluster was still installed

 

[luv2rallye]

Oh, ok. I was worried you meant 1 ohm to ground. But ya, 1 ohm (or usually less) between connector pins that are supposed to be connected is good.

What is the ohms between PTU pin 4 and cluster tacho gauge (white wire, connector C-05 pin 24) both with tacho plugged in and unplugged?

 

[lololobster]

Have you tryed testing the cluster tacho gauge (white wire, connector C-05 pin 24) with your voltmeter freq setting while engine running? If no signal when plugged in, do you see it there with it unplugged?

I just tried this and got nothing…

Oh, ok. I was worried you meant 1 ohm to ground. But ya, 1 ohm (or usually less) between connector pins that are supposed to be connected is good.

What is the ohms between PTU pin 4 and cluster tacho gauge (white wire, connector C-05 pin 24) both with tacho plugged in and unplugged?

pin 4 and c-05 pin 24 has .6 ohms with tach both plugged in and unplugged

 

[luv2rallye]

Ok. So the wires show continuity to the tacho which is good, but your meter shows nothing on the freq setting on cluster tacho gauge (white wire, connector C-05 pin 24) with engine running whether that C-05 connector is plugged in or not - all with engine running? I would think you'd see the signal at least with it unplugged. For freq test you're measuring the signal to ground correct?

 

[lololobster]

your meter shows nothing on the freq setting on cluster tacho gauge (white wire, connector C-05 pin 24) with engine running whether that C-05 connector is plugged in or not - all with engine running?

correct, its hard to get a backprobe in the connector with the cluster installed but yea nothing on frequency

For freq test you're measuring the signal to ground correct?

correct, straight to battery ground terminal

 

[luv2rallye]

Well I'm a little surprised you don't see freq on C-5 with it unplugged but there's probably some reason (like maybe C-05 powers something else that's needed - although you said you saw freq on PTU pin 4 with C-05 unplugged correct?).

At this point I'd say your tacho gauge is suspect although you tryed 2 of them correct? Do you absolutely know if those were the correct ones (for your year of wire harness - at least 2ga vs 2gb) and working before trying them?

I suppose there's a small possibility that the PTU is outputting garbage and that's why the meter reads something (on freq setting) but the signal is not correct for the tacho to function. You'd need an oscilloscope to look at the signal to verify which I'm sure you don't have. However you said you already tryed 2 PTU's so you'd think that's not the problem.

 

[lololobster]

Well I'm a little surprised you don't see freq on C-5 with it unplugged but there's probably some reason (like maybe C-05 powers something else that's needed - although you said you saw freq on PTU pin 4 with C-05 unplugged correct?).

so i just went out to double check, but now the only way i see frequency on anything is if the negative lead is unplugged. with the negative unplugged i see frequency on both pin 4 at ptu and pin 24 c-05 on positive lead. all with cluster unplugged and ptu plugged in

At this point I'd say your tacho gauge is suspect although you tryed 2 of them correct? Do you absolutely know if those were the correct ones (for your year of wire harness) and working before trying them?

one of them definately used to work, but now i hear some stuff rolling aorund inside so im suspect. the other cluster i have no history of

 

[luv2rallye]

With the negative lead unplugged, any freq you read is most likely just low level noise and give you a false reading and should be ignored.

 

[lololobster]

With the negative lead unplugged, any freq you read is most likely just low level noise and give you a false reading and should be ignored.

yea now i cant get a frequency reading off either of my ptus when backprobed, both cluster in and out

 

[luv2rallye]

Ya when backprobing it's always hard to know if you're really touching the metal pin or not with the wire in there.

 

[lololobster]

Trying to revive this as the problem is not fixed yet,
Aswell as no tach the car also has no speedo and in turn odometer, however i see speed and rpm in ecmlink when datalogging, could this be meaningful???

 

[luv2rallye]

ECMlink I hear gets rpm and speed from a different source than the cluster so it's not meaningful.

I suppose you could try stringing your own wire from PTU pin 4 to C-05 pin 24 (and disconnecting the wire that is there) to see if the tach works.

 

[lololobster]

ECMlink I hear gets rpm and speed from a different source than the cluster so it's not meaningful.

I suppose you could try stringing your own wire from PTU pin 4 to C-05 pin 24 (and disconnecting the wire that is there) to see if the tach works.

ecmlink doesnt get its speed signal from the VSS?? odd

i also tried to read the frequency on pin 14 of the OBD2 port and got nothing when i would spin the tires


at this point i just want the tach to work, i might just de pin and rewire it all

 

[lololobster]

OK ITS FIXED

my c-05 connector was completely flipped upside down in its holster, i thought i had the wrong cluster or diagram but i flipped it and everything works now, i have no idea how someone could have done that

 

[luv2rallye]

I'm sorry I misled you. The 2.0 turbo ECU does get it's speed signal using the VSS - it comes in on ECU pin 86.

You can check the VSS by looking for pulses on the data link (OBD2) connector pin 14. Jack up front of car, block one wheel from turning (so that wheel doesn't just rotate backwards and not turn VSS in tranny), turn key to on (engine not running), and manually turn other wheel very very slowly (like only inches/second). Should see pulses on an analog (needle) meter on DC setting. Usually you won't see anything on a digital meter DC setting because the pulses come too fast (or not fast enough) and the meter will just average it (although you should see some reading [11v or 0v] if you stop the wheel every few inches). Pulses go between 11v and zero (you'll see when wheel is stopped) and you'll get about 5 pulses/rev. You can't use the AC setting because that assumes the signal is a sine wave which it isn't plus the frequency is way to low to be detected properly. Or you can drive the car very very slowly and monitor pin 14 with analog meter DC setting. Doubt you'd see anything on frequency setting as the freq is too low.