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Error P0134, lean at idle, no power at drive

  • Adam Pyka
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25 Nov 2021 10:13 #240319 by Adam Pyka
Hello,
I've a Jimny 1.3 16V VVT (2009) and the problem with error P0134 - O2 sensor circuit no activity detected.
Each time the engine is idling it goes to lean condition, upstream O2 sensor gives voltage slightly above zero volts. The short time fuel trims goes high to about 20. 
At first I checked the valve clearance - it is set as in the workshop manual. The cylinder compression is also in the proper range.
Than I changed the: spark plugs, hi-voltage cables, coils, injectors, MAF sensor and MAP sensor. No difference.
I double check the vacuum - solenoid valve, PVC valve. Also I checked the intake leaks, I can't find any visible signs...
Next I checked the exhaust system, changed the old sealing between exhaust pipes, checked the flow. No difference.
Finally I bought new O2 sensor (Denso DOX-0113) and still no difference!
If I accelerate to 2000RPM the sensor react to 0.9V, than oscillate few times 0.1-0.9V and goes low with STFT going back to 10..15.
During normal car drive I can feel lack of power so the engine is probably running lean.

What may cause such an issue? I'm in the totally in the end of the ideas. Below the screenshots from Torque.

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25 Nov 2021 14:24 #240324 by DrRobin
P0134 is the up-stream O2 sensor, I am a little unsure which one you changed, but if it was the upstream then it could be a wiring fault.

Looking at your graphs, if it isn't the sensor that is faulty, then it is the wiring, most likely the heater circuit on the O2 sensor as you said it goes up to 0.9V under acceleration and then shows the normal oscillation (lots of hot exhaust gases going through warming up the sensor), but drops back down to low voltage at idle when it cools down.

O2 sensors have an inbuilt heater element as they need to be very hot to work correctly.

Fuel (rich/lean) is set as follows:
- The MAF says how much air is entering the engine
- The ECU adds fuel at a ration of 14.7 air to 1 fuel
- The upstream O2 sensor then fine tunes the ratio
- The fine tuning is seen as a fuel trim, both short term and a long term average.

When idling the upstream O2 sensor ocillates from rich to lean, several times per second, but tools like Torque will only show it less frequently as the ECU can't send the data fast enough.

The downstream O2 sensor doesn't change the fuel/air ratio, it is just there to monitor the effectiveness of the CAT. If the downstream sensor changes as rapidly as the upstream sensor the CAT is faulty. A steady line on the downstream sensor indicates the CAT is working correctly.

Your upstream O2 sensor is very low most of the time, this indicates a lean mixture and pushes the fuel trim up to the maximum. If it is a faulty sensor, your car will be running very rich and will be fouling the plugs, all this fuel and fouling of the plugs would give poor performance.

2020 blue SZ5
Ex 2011 Blue Jimny SZ4
Northumberland Jimny Blog

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  • Adam Pyka
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25 Nov 2021 15:03 #240326 by Adam Pyka
Replied by Adam Pyka on topic Error P0134, lean at idle, no power at drive
Thank You for the answer. I changed the upstream O2 sensor.The O2 downstream sensor looks to work great since if the upstream oscillates (when driving) the downstream stays steady.

If it is a faulty sensor, your car will be running very rich and will be fouling the plugs, all this fuel and fouling of the plugs would give poor performance.

I'm quite curious why downstream sensor is also lean rather than reach if the STFT is high?Nevertheless I'll try to check the voltage directly on the wires by the oscilloscope. Some more screenshots in the attachment.
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25 Nov 2021 15:22 #240327 by DrRobin
Looking at your latest graphs these look normal, O2 sensor 1 oscillating over 80% of the range and downstream fairly steady.

I wouldn't worry about the downstream sensor been a small bit on the low side, as far as I know it isn't used for anything other than checking that the CAT is working correctly.

I have Torque on my 2011, I can't remember what the downstream O2 sensor reads, it might be a bit more than yours, but not a lot, I could try to get a picture tomorrow?

I checked the O2 sensor you fitted, Denso DOX-0113, this comes up as a universal part, it is a sensor with a wiring kit for you to splice on to the original cable and connector. I recently fitted these to my other car and was then warned that the crimp up connectors are not very reliable, so I changed all four to the correct part with the connector already fitted.

It could be that you either have the wrong O2 sensor or have a bad connection on the 'made up sensor'.

I will try to find the original sensor part number for your car.

Robin

2020 blue SZ5
Ex 2011 Blue Jimny SZ4
Northumberland Jimny Blog

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25 Nov 2021 15:44 #240328 by DrRobin
According to a cross reference a Denso DOX-0354 is the correct part number for pre-CAT and DOX-0350 for post CAT.

Search on Google, they are around £55 in the UK. A word of warning, a number of sellers with UK sounding names are owned by a company called AutoDoc, they ship out parts from Germany and take 7 - 10 days to arrive, despite what they say on the website.

There are a few UK suppliers, they might be a couple of quid more, but you can get them next day.

2020 blue SZ5
Ex 2011 Blue Jimny SZ4
Northumberland Jimny Blog

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26 Nov 2021 09:47 #240336 by DrRobin
Hi,

I have attached a couple of photos from my 2011 Jimny showing the O2 sensors.

The first two were taken on the open road doing just less than 60mph and were taken about 3 miles from home so the engine wasn't really up to temperature.
 
 

The last was taken at idle after a 10 mile journey. 
 
The post CAT sensor was a little lower when it first started to idle and you can see it slowly rising, but it doesn't get back up to the same level as seen when pulling 3,000rpm.

A lowish reading post CAT at idle is very likely normal, it just says that some of the O2 is been used to reduce or oxidise the harmfull gases.  The output of the CAT should be Carbon Dioxide.

Robin

2020 blue SZ5
Ex 2011 Blue Jimny SZ4
Northumberland Jimny Blog

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  • Adam Pyka
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29 Nov 2021 23:01 #240404 by Adam Pyka
Replied by Adam Pyka on topic Error P0134, lean at idle, no power at drive
Just returned from the garage. I checked the voltage across the heater (after final connector so the real voltage that reaches the heater) and it looks like a PWM signal from 0V till battery voltage (see the attachment). Is it good? I thought that it is stable 12V rather than pulse.Than I checked the O2 sensor voltage (before the final connection so from the side of ECU). At the begining of idling it fluctuates, than it stabilized to reach about 100mV when engine coolant reaches 70-75deg. Than the oscillations can be observed ONLY if I accelerate to 2k RPM or more.Any ideas what to check?

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30 Nov 2021 11:49 #240408 by DrRobin
I have never measured the the heater circuit, but it seems that it is likely to be PWM, see the following article

www.picoauto.com/library/automotive-guid...irconia-with-heater/

According to the article, the ECU controls the power to the heating element, but I don't fully uinbderstand what it measures, is it current and realises when the O2 sensor is warm or does it measure [exhaust gas] temperature?

It makes sense to control the heater element, running it when it is not needed would only shorten the life. Anyway your waveforms could be correct.

The article does mention something else, is your engine running in 'Closed Loop' (using O2 sensor) or 'Open Loop', just add the fuel status object to your Torque screen.

At idle and under normal driving, you should be in closed loop. When accelerating [hard] or when engine breaking you go in to open loop as the O2 sensor is not a reliable way of setting the mixture under these two conditions.

Where next, well I would check the plugs to see if it is running rich or lean, that might help determine the next step. If it is running lean, this confirms the Lambda sensor and this is often a vac leak, exhaust leak, or fuel filter/pump issue/injector issue.

Basically either your Lambda is working correctly so something else is causing the problem or it is still giving wrong readings in which case it is telling the ECU to put the wrong amount of fuel in.

2020 blue SZ5
Ex 2011 Blue Jimny SZ4
Northumberland Jimny Blog

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01 Dec 2021 11:15 #240420 by LesNewell
Just a thought - is your coolant level dropping at all? Antifreeze kills O2 sensors very quickly and when they die they give similar symptoms to what you are seeing. I've seen this a few times on cars when the head gasket goes.

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  • Adam Pyka
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01 Dec 2021 12:16 #240423 by Adam Pyka
Replied by Adam Pyka on topic Error P0134, lean at idle, no power at drive
The engine is running in "Close loop" at idle, only I can see "Open loop" when hard accelerating or at first sec when engine breaking.
There is no coolant leakage, the same stable level. The O2 sensor was replaced to new one Denso DOX-0113 without any results.

Please take a look at the spark plugs, cause I'm not so skilled to evaluate if the mixture is lean or proper. Photos show spark plugs from cylinder one and two.

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01 Dec 2021 13:07 #240424 by DrRobin
Hi,

I would have said the plugs look normal, see the following chart

www.atvriders.com/articles/how-to-read-spark-plug-colors.html

The Open loop/closed loop sounds normal as well. Once the sensors are warm it should be in Closed Loop most of the time, except hard acceleration (the O2 sensor is unreliable at setting the fuel ratio) and when engine breaking, there is no or very little fuel injected.

I am still wondering if you have the correct sensor, a DOX-0113 is a universal sensor and whilst it lists a Jimny as compatible, the crimp connectors are known to cause problems.

If it isn't the O2 sensor, or a head gasket, then it might be a fuel issue or one of the other sensors, most likely the MAF.

If you disconnect the MAF, it will run on the inbuilt map in the ECU, if this runs better then suspect your MAF.

2020 blue SZ5
Ex 2011 Blue Jimny SZ4
Northumberland Jimny Blog

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  • Adam Pyka
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01 Dec 2021 23:55 #240435 by Adam Pyka
Replied by Adam Pyka on topic Error P0134, lean at idle, no power at drive
I found the waveform summary in the Jimny Service Manual, the O2 output waveform at idle definitely should be different whereas the heater circuit looks great (see attached file). I disconnected the MAF and the engine runs without big difference whereas the O2 goes very reach. Tomorrow I'll check the MAF by the scope but I re changed it with other (Denso DMA-0113) and the problem was the same, maybe the wiring issue?
How about the fuel system, maybe should I change the fuel filter? The car has about 230.000km and nobody change it before...
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