Engine only runs with throttle position sensor disconnedted??

Mark Le Rouret

Mark Le Rouret

My K12 1.2 will only start if I disconnect the throttle position sensor (TPS).
So I replaced the throttle body (with TPS integrated) but still will not start unless the TPS connector is disconnected.
Throws no error codes with TPS connected.
 
The accelerator sensor seems to be on the same circuit, because if when I disconnect the TPS it throws error codes for bot TPS and pedal position sensor.
If anyone has any ideas on this I would be eternally grateful.
Cheers,
Mark
 
thats the nature of drive-by-wire mark
maybe the pedal sensor is faulty ? (stuck full open or whatever)
so the ecu flags a shutdown mode, and disconnecting the tps allows a limp home mode
 
Thanks for your response Frank,
The pedal seems to work in that it will rev the engine when running.
Is it worth just changing the pedal sensor, or is there a way to test it?
 
you need a data lead or obd bluetooth ideally mark
to read the live outputs of the sensors
there is a pedal dance to sync the throttle too iirc
 
.... a development... the engine now runs with the TPS connected, but reving up and down as you would expect with it not connected.
Maybe it's an intermittent fault and fiddling has changed it somehow.

The ECU throws no error codes with the TPS connected. With it disconnected I get all the throttle/pedal sensor errors you would expect.
I tried the throttle dance procedure, but maybe Im doing it wrong... but it would still run without this right? Just not correctly?

I also dismantled the pedal and all looks good in there.... just four resistance tracks on a printed circuit that look ok mechanically, but there may be an electronic component failure?
 
I kept persevering with the relearn procedure as quoted on this forum, and it gradually got better and better.
Now idle is around 900 which is normal.
So this reset problem was masking the fact that I fixed the original fault by replacing the fuel pump.

Thanks to you Frank I fixed it.... get in!!
 
Hmm.... it was really reluctant to start this morning. It's like it has forgotten the relearn thing, but not completely.
I did the relearn again and now seems fine again, but of course it's warm and easier to start...

Any ideas Frank?
 
Ran it loads yesterday and it ran normally and started normally all day.

This morning will not start at all!!!

Did the relearn a number of times and still will not start!!
What is going on?

This is frustrating the hell out of me...
 
I have a replacement throttle body. I am tempted to put it on, but I have no confidence it will fix it.
To me its a config problem that is intermittent.
 
I changed the throttle body and makes no difference at all. Just will not start.
What can have changed overnight. Goes from starting and running normally in the evening to nothing the next morning.
 
Got to thinking it must be temperature related, so opened the bonnet/hood and left the car in the sun all morning.
Sure enough it started!! and the idle speed was good so the relearn was saved!!

Not that its cold at night. Got down to about 18 C/ 65 F last night.

Any ideas what that could be?

Doesnt have to be the throttle body thing... maybe another unrelated fault.

I previously changed cam position, crankshaft position, MAF sensors and battery is in good condition.
 
OK cool. I already changed the MAF.

I removed the connector for the coolant temp sensor and it throws a code. So the wiring is good.
No fault code when its connected but I am guessing on a car of this age the fault reporting is not that sophisticated, so it could be faulty and not produce a code?

Not sure a faulty temp sensor would prevent it starting, but at 10€ I ordered a new one.
In France delivery is expensive and pants so could take over a week.
 
Right... I read on this forum that the coolant temp sensor is an input for the ECU for cold starting etc. so I understand that if it was faulty would cause starting problems.

I am waiting for the new sensor to arrive, so removed the old sensor and tested it against these figures I found on this forum:
The ecu coolant sensor should read-
0.25 ohm @ 90c
0.85 ohm @50c
2.5 ohm @20c

My sensor gives:
0.3 k ohms @ 85 c
2.4 k ohms @ 24 c
Which looks about right except that forum figures seem to be a factor of 1000 out, wich I am guessing is a mistake.

So it looks as if my sensor is working unless anyone knows different?
 
looks ok to me mark
you could try a drop of fuel on the airfilter on a morning startup (to rule out a starvation or lack of coldstart enrichment)
might be worth checking the chain tensioner too ?
or cam sensor problem that is confusing the 720deg sequential signal
 
ce
frank said:
probably combined with the maf mate
Click to expand...

Hi Frank,

Is it possible all this could be due to timing chain stretch? I read alot about it for the K12.
But when it was running recently, for a couple of days (after the throttle position relearn), it was running and starting great, plus I have no error codes.
If it was timing chain it wouldn't be intermittent right?

I have changed so much stuff, fuel pump, cam, crank, MAF sensors, throttle body, plugs, ECU.... and been working on it on and off for nearly six months.
A local garage gave up on it, and the Nissan dealer told me it needed a new engine!!!

I am coming to the point where my only option is to scrap it.
I grieves me cos I have owned it since new and it is in really good condition.
I know its a minor fault but just can't find it.
My theory is that the ECU is not getting all the correct inputs, but its intermittent.

Can you think of anything at all that it might be?
 
the non starting from cold needs to be picked apart really mark
if you rule out fueling/starter motor/battery (drop of fuel and bump start) then i would be checking the 720 reference (ie, is it sparking at cyl 1 on the correct tdc)
 
Have you tried the few drops of fuel on the air filter in a non-start situation as Frank suggests & also checked the chain tensioner run out?

Apart from intermittent PSU wiring/plug/socket corroded connections, the following well documented common K12 faults may give rise to non-start issues

Quote:

13-1-2011: “2004 Micra has been recalled due to a recent 'safety concern'. Apparently, there is a possibility that an electrical contact within the ECU ( on a relay) may become contaminated with silicon oxide, which could cause the engine to stall and make re-starting difficult”.

3-3-2012: “Notorious fault is severe corrosion of the fusible link holder, which is situated underneath the nearside headlamp unit. Rated at 30 amps, this piece of cheap and nasty, plastic framework (costing £64.97 ) suffers from very poor design of the waterproofing housing which results in moisture build-up inside the housing”.

Reference: https://www.honestjohn.co.uk/carbycar/nissan/micra-k12-2003/good/
 
frank said:
the non starting from cold needs to be picked apart really mark
if you rule out fueling/starter motor/battery (drop of fuel and bump start) then i would be checking the 720 reference (ie, is it sparking at cyl 1 on the correct tdc)
Click to expand...

OK.... put petrol on the air filter and it started almost immediately then continued to run even when I removed the filter.
It ran smoothly and also restarted after I stopped it. Idle speed normal.

So this looks like " lack of coldstart enrichment " right?
What would cause that?

I do have the Check Engine indicator on, but no error codes.
 
Ft
plmval said:
Have you tried the few drops of fuel on the air filter in a non-start situation as Frank suggests & also checked the chain tensioner run out?

Apart from intermittent PSU wiring/plug/socket corroded connections, the following well documented common K12 faults may give rise to non-start issues

Quote:

13-1-2011: “2004 Micra has been recalled due to a recent 'safety concern'. Apparently, there is a possibility that an electrical contact within the ECU ( on a relay) may become contaminated with silicon oxide, which could cause the engine to stall and make re-starting difficult”.

3-3-2012: “Notorious fault is severe corrosion of the fusible link holder, which is situated underneath the nearside headlamp unit. Rated at 30 amps, this piece of cheap and nasty, plastic framework (costing £64.97 ) suffers from very poor design of the waterproofing housing which results in moisture build-up inside the housing”.

Reference: https://www.honestjohn.co.uk/carbycar/nissan/micra-k12-2003/good/
Click to expand...

The petrol on filter started it see my reply to Frank.
I runs smoothly so i'd like to think we can rule out the timing chain. What do you think?
This would be a gradual degradation of performance right which I never had.

I bought a replacement ECU (cloned from my own) from CarTech. This didnt fix it, but it did run for a while.
That is a great service btw. I returned the replacement to them and they only charged me a "rental" fee.

I did go in the fuse box under the headlamp to check the fuses and relays and didnt notice anything unusual.
 
frank said:
coolant temp sensor usually mark
might be a fuel pressure or leakback problem tho ?
Click to expand...

The coolant temp sensor checks out ok when I tested it, but I have a new one on order.
I installed a new fuel pump, and there is pressure in the line. It sprays out everywhere when I disconnect it.

What is leak back?
 
frank said:
sounds like your codereader is,nt suited to your car either
Click to expand...

Bought this Autolink AL319 reader under a year ago.
Do you mean if the Engine Check light is on it should detect a code?
 

Attachments

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frank said:
a drop of pressure overnight mark
and some generic readers dont function properly on some cars, i think k12,s included
Click to expand...

Booked the car in for its (French) MOT this morning. Started the car with the petrol on filter trick no problem first thing.
So set out for the MOT, just out of the gate engine starts coughing and Check Engine light comes on.
You couldn't make this stuff up!!!

So back home and check the codes and get Crankshaft Position Sensor code. I already changed this sensor.
The only time I have seen this code before is with Crankshaft PS disconnected.
I did have the air con on full and I know this puts extra load on the engine.

Left it for a while, and went for a run and its fine again, apart from the odd random cough.
Tried it with and without a/c and made no difference.

What do you think?
 
frank said:
i would get that code read with a pro reader mark, you might be getting wrong codes flagged up
Click to expand...

Is there a known reader that works on the K12 that I can buy? Otherwise I have to find a garage.
I can't go the Nissan dealer, they told me it needed a new engine!!! useless.

If it was a Crankshaft PS fault, would that suggest it's the timing chain? or is that normally associated with a Camshaft PS fault?
It's done 118k miles, would chain stretch normally have happened way before now?

Is it difficult to check for timing chain stretch?
 
Quote:
“I did go in the fuse box under the headlamp to check the fuses and relays and didnt notice anything unusual”.


Trouble service bulletin: 3-3-2012: “Notorious fault is severe corrosion of the fusible link holder.

Location stated appears to be incorrect or a similar cheap electrical tat item now appears to be located down the side of the battery attached to the positive terminal.

This troublesome cheap tat fusible link holder is also a known to be a possible source of intermittent starting & running issues that you have.

NB; As Frank suggests, disconnecting the power supply fusible link assembly or the battery, to reset ECU, can lead to imobiliser/ radio loss of key/security codes!

References:

 
Last edited:
plmval said:
Quote:
“I did go in the fuse box under the headlamp to check the fuses and relays and didnt notice anything unusual”.


Trouble service bulletin: 3-3-2012: “Notorious fault is severe corrosion of the fusible link holder.

Location stated appears to be incorrect or a similar cheap electrical tat item now appears to be located down the side of the battery attached to the positive terminal.

This troublesome cheap tat fusible link holder is also a known to be a possible source of intermittent starting & running issues that you have.

NB; As Frank suggests, disconnecting the power supply fusible link assembly or the battery, to reset ECU, can lead to imobiliser/ radio loss of key/security codes!

References:

Click to expand...
Thanks for that.
I checked it out, see photo,
Only superficial corrosion. The top link is also fine although not shown in the photo.
Inevitably broke the transparent plastic cover. Really bad design. Lashed it up with some cable ties.
20200625_110911.jpg

The batter has been disconnected too many times during this protracted affair!!
 
frank said:
that short term fuel trim does,nt look right mark
need a copy nissan consult really
Click to expand...

Thanks Frank.

Crankshaft PS fault code turned out to be correct. I had already changed the sensor (for a used part from ebay), so I change it back to the original and the coughing and the code went away. So I had introduced another fault with a used part.... I despair.

New coolant temp sensor arrived and fitted yesterday. No change.
I tested both the new and old for resistance at 20c and they are similar, so no big surprise.

Is there a cheaper workaround for Consult 2, it would be around £150 plus cable, and with my luck on this may not give me a result!
 
Mark Le Rouret said:
My code reader gives me no fault codes but gives an AMBER warning, and no explanation.
Would the torque app detect that?
Click to expand...
never worked on a k12 tbh mark, i think its pot luck with generic readers or apps
maybe the cts is working ok but not communicating with the ecu ?
 
Had trouble with my first code reader it was Bluetooth got no connection tried loads of times.
Just recently got the streetwise Wi-Fi one and it connected within a couple seconds.
Not sure if that says the scan tool was a problem or just the dongle and connection to ecu.
Cannot really say if it will find codes but it should do better than the one that wouldn't connect.
Hope this is of some help to you.

Sent from my ASUS_T00P using Micra Sports Club mobile app
 

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