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Tigra Twintop 1.8 AT Z18XE AF17
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Discussion Starter · #1 · (Edited)
Explanation of C1500 fault code for the Electric Power Steering EPS.
Applicable to Meriva A, Corsa C, Tigra B, possible Meriva B but I don't know for sure.

C1500 means Invalid Torque Sensor Signal. Which are actually 2 potentiometers inside the steering column assembly.

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Fault code set criteria, the output signal of any of the potentiometer 1 or 2 above 4.5V or below 0.5V at terminals 4 or 8.

Repair manual says either torque sensor defect or the EPS control unit.

This is the electrical diagram.

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Wire colors Violet and Blue.

To proper diagnose this, I set an oscilloscope to these 2 terminals, measured against battery minus.

There is no way this can be diagnosed with a multimeter, neither with processed diagnostic data, forget about it, at least not how this vehicle behaved.

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This is how the reading looks like, when turning the steering wheel. Signals should be in opposition to each other, you can clearly see that the blue line, blue wire pin 8 shows a dirty potentiometer track or even maybe carbon track wear and tear. Also pretty obvious its signal goes below 0.5V, you should of seen the steering behavior, sometimes even turning by itself.

Now, these are filtered channels, EPS will filter as well, but both signals were pretty noisy.

Conclusion: defect torque sensor assembly. It is sold as a separate component.

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Good info there.
Often wondered what was inside that torque sensor.
I've a spare column with ecu and motor which am hoping to fit to a classic Ford at some point so this is a good start.
 

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Discussion Starter · #3 ·
You would need a vehicle speed signal and engine speed signal in pwm format. I have a video on that engine speed signal:

 

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Thanks for posting that most appreciated.
Getting an engine speed signal wouldn't be a problem as I'm using a trigger wheel on the engine for a standalone ecu. The car speed is going to be more difficult as there's no electronics involved! Maybe a toothed gear something like an ABS ring?
 

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There is an EPS thread on here somewhere which shows the torque sensor dismantled.
 

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Discussion Starter · #6 ·
Thanks for posting that most appreciated.
Getting an engine speed signal wouldn't be a problem as I'm using a trigger wheel on the engine for a standalone ecu. The car speed is going to be more difficult as there's no electronics involved! Maybe a toothed gear something like an ABS ring?
Older cars had a converter build into the instruments, where the mechanical speed cable came in, from the gearbox. Or on the gearbox itself.
 

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Thanks for that, very interesting.

What I'm unsure about though is what circumstances cause the EPS system to go intermittent?

I understand that potentiometers of all kinds (commonly wire wound or carbon film) go intermittent because they simply wear out, or break (carbon film) and that if when the EPS system was initialising it may check for specific voltages (that could be way out if the wiper is dirty or the resistor broken etc) or agreement between both pots (if there are two in parallel for safety etc) and that there could be a different failure condition between starting and in use.

But I noticed that I first posted about the / my classic 2004, 75k miles Meriva ESP fault back in 2013 when I was first given the car by my Mum when my Dad died and I have been driving it fairly regularly since. The EPS fault has re-appeared now and again and across a wide range of uses, conditions and temperatures but for the first time ever yesterday, simply switching off the ignition and turning it back on again didn't restore good EPS. I even drove the car around the block to give the battery a chance to pick up a bit but that made no difference.

I even stuck my Lithium jump-start pack pack across the battery in case the voltage was dipping on start (it still spins over pretty fast and starts quickly in any case etc) but still no EPS.

I left the car a couple of hours, connected up OpCom ready to see why it was now 100% dead and of course it worked perfectly and continued to do so though the day of multiple stops and restarts?

I even recorded the steering measuring blocks on the initial trips, fairly sure tit was going to fail at some point but no. (Edit: I did see / clear two error codes, C1532 and 1500, no surprise there?). ;-)

Two things I want to do before considering replacing anything on the steering. Check the battery / alternator (a mate has a tech tool just for that I can use that even gives a printout) as I can't remember the last time the battery was replaced ... and try cleaning all the connectors associated with the torque sensor as it appears from reading here that has cured the issue for some.

The most common fault scenario for this EPS recently is after first starting after being left a while (overnight or when visiting etc). Drive for a few a few seconds and then the EPS light comes on and all PS drops out. Turn off the ignition, turn it back on again and all is well for the rest of the trip.

When it failed yesterday I first tried it at about 07:00 and then again at 09:00 (when it worked all by itself (when it was also slightly warmer?)).

I have been a(n IT) support guy all my life and when repairing all sorts of gear, from datacomms to TV's, part of my test toolkit along with a multimeter, scope and BERT testers were the use of vibration / shock (often a screwdriver handle <g>), time (running an error test overnight), heat (hot air gun) and cold (freezer spray), flexing / movement (wires / PCB's), along with general observation (burnt components / bulging caps / dry joints) I have revealed many intermittent faults. I was wondering which of those I could apply to the Meriva and where?

The last time the Meriva ECU failed I was able to very precisely duplicate the fault situation (failure to start because of an immobiliser issue) by applying heat with a heat gun to the ECU. Hot or cold it would start fine, warm it wouldn't.

I was going to say 'bring back contact breaker points' but the first and about the only technology upgrade I did when we built the kitcar, outside of fitting an electric fan was the opto-triggered electronic ignition. ;-)
 

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The Meriva Owners group on Facebook has a very useful guide to resolving faults with the EPS.
It does however sound like a failing battery, alternator, or both.
 

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The Meriva Owners group on Facebook has a very useful guide to resolving faults with the EPS.
Oh, thanks, I'll check that out.

It does however sound like a failing battery, alternator, or both.
Hmm, I'm guessing it isn't full capacity but (as I'll explain in a sec) I don't think it's 'bad' because I've been spinning the engine over quite a bit very recently [1] and it's been doing quite a few stop / start runs (errands and moving home etc) and so I think the alternator is still ok?
[1] So, we took the dog for a walk for an hour or so and when we got back to the car it wouldn't start because it was immobilised (car with spanner flashing after about 5 seconds). Wiggling the leads into the ECU seemed to allow it to start after but then it wouldn't start again shortly after (seconds).

Disconnected the battery for 10 seconds, no different, left the battery disconnect 10 mins, nothing better, left the battery off 20 mins (still waiting for the AA) and it started so we took the chance that it would only stop it starting, rather than kill it once started and drove home (only a couple of miles). I tried to start it a couple more times once home and it did, so I'm wondering if we have regained the ECU problem we had 8 years ago where it wouldn't start when warm, but was ok when hot or cold?

I'm just having a cuppa then I'll stick OpCom on it and see if my neighbour / mate can stick his starting / battery diagnostic unit on it with me.

Oh, no ESP issues all day after a range of speeds / temperatures and numerous stops etc?

(I ordered some DeoxitD5 yesterday to clean the torque sensor connector with the promise of it being delivered from the 1st and it arrived this morning)!

.<some time later ...>

Well, it won't start again (immobilised) and OpCom can talk to the BCM, Immobiliser and EPS but can't talk to the ECU?

I think I'll take a closer look tomorrow.

Just remembered, I saw error code B3040 on something .. (when immobilised).
 

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Discussion Starter · #13 ·
You say you have a scope, put it at work, then replace the torque sensor if needed and enjoy some more mileage.
 

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Yes, I do have a USB scope and thanks to your info I can 'put it to work', [1] following along with your 'why' title. ;-) But my question wasn't really how can I test it but what could cause such an intermittent fault.

The problem has now mutated because the EPS won't work if the engine won't start and the engine won't start if it thinks it has an immobiliser issue. ;-(

When I managed to get OpCom to access the ECU I saw a P1612 error code.

Tomorrow I will try to check / clean all the connections (ECU / immobiliser / dash / EPS) and the check battery / alternator condition in the hope I can get back to my EPS issue.

[1] I also have a voltage datalogger that I could use to monitor the raw voltage outputs of the torque sensor.
 
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