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Torque » Torque OBD ECU Scanner » Torque Discussion / Ideas » Occasional - but avoidable P0135 (O2 heater ckt err)

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Author Topic: Occasional - but avoidable P0135 (O2 heater ckt err)
F-150Torqued
Member
Posts: 437
Post Occasional - but avoidable P0135 (O2 heater ckt err)
on: April 19, 2015 (GMT)

Occasional – but avoidable P0135 (O2 heater ckt err)

@crok;

I am responding to your last post in “Rich to Lean sensor threshold voltage(constant) fails – P0420?” in this new thread because the TOPIC there has drifted of point so far it is not be helpful to members with P0420 Rich / Lean problems, OR P0135 O2 sensor heater problems.

‘QUOTE’

Quote from crok on April 19, 2015 – In the Prior Thread –
So far so good, 1 week without the Magical Illuminating Lamp.

A trick that may be helped for me:
I explained how the O2 sensor heater test works and how I
tested the heater circuit. So an idea came to my mind and
before starting the engine I just turn the key on for 15..20
seconds, allowing current to flow through the O2 sensor heater
element without/before starting the engine. I’m not sure that
this is the trick and/or the cabling/connection of the coolant
temperature sensor or both.. but seems working.

‘END QUOTE’

Let me say again, I do like your diagnostics style. Since part of the detailed discription of DTC P0135 is that the O2 sensor took TOO LONG to reach proper “operating voltage” – which is apparrently based on the Coolant sensor temperature reaching a certain point – your test is especially helpful.

It sounds more and more like the O2 sensor (even though recently changed) may be defective. It does happen. Only remaining suggestions I have before changing out the O2 sensor would be:

1) use a good spray electrical connection cleaner on ALL connection involving both O2 sensor (B1S1) and the Coolant sensor. I understand the O2 sensor may be fused, so that connection could also have high resistance. I would also clean and re-plug the ECU connectors.

2) It would not be expensive or hurt to drain and flush the Coolant system and refill with proper mixture of quality coolant. When I did that on my vehicle (around 180,000 miles), the temperature gauge actually read a few degrees higher – near the rated thermostat temp. (can’t honestly say I ever paid any attention to the TIME though).

PS. Your English is just fine!

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54371019
crok
Member
Posts: 15
Post Re: Occasional - but avoidable P0135 (O2 heater ckt err)
on: April 19, 2015 (GMT)

@F-150Torqued

I own the car since a year only.. I did not know anything about the car’s history (at least I did not trust what I have from the last owner).. so I asked the mech. before winter to flush the coolant and fill it with proper coolant mixture – thus option two is already done I think. So, IMHO the O2 sensor is less likely the cause but you are right, it can be the cause – thus I decided to do the first thing you mentioned: reconnect all electric connections after a proper cleaning of the plugs and connectors. If that does not help I will go back to the mech. and replace the coolant temp. sensor and the thermostat and check the wiring and the fuse as well (just to be on the safe side..). If that does not help I should change the O2 sensor.. I would like to avoid an unnecessary change of a really expensive part of the car (a new one costs approx. 8% of the price of the whole car..). I will update the thread if I did the connection cleaning. (I have to go to the UK for a week on Monday but I really looking forward to do it.)

Seat Toledo 1.6 16V (2001 – AZD engine code)
F-150Torqued
Member
Posts: 437
Post Re: Occasional - but avoidable P0135 (O2 heater ckt err)
on: April 19, 2015 (GMT)

^^^^X2. I understand. Good luck

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54371019
crok
Member
Posts: 15
Post Re: Occasional - but avoidable P0135 (O2 heater ckt err)
on: May 6, 2015 (GMT)

Update: the code came back again and again after I cleaned almost all connectors and plug.. Yesterday I decided to change the coolant temperature sensor, I explain why: one morning I decided to fire up Torque and put these on the same screen in real time data: coolant temperature, intake air temperature and pressure, B1S1 and B1S2 O2 sensor voltage, short and long term fuel trim and (I guess the most important from the decision point of view) the *fuel system status*.

So, Torque connected to the ECU, fuel system went to closed loop after 15 seconds.. rolling into the street.. gentle cruising.. and after a while I noticed the following in Torque (and on my dashboard): check engine light on – code P0135 – and fuel system status shows “open loop, insufficient engine temperature” while the coolant temperature OBDII *value* says 90°C.

So this is what is happening I guess: the O2 sensor heating test fails during the ride because out of the sudden the engine temperature became “insufficient” and ECU recognises this as the O2 sensor’s heater element is not working properly because “if the ECM determines (based on coolant temp) that too much time elapsed before the oxygen sensor began operating properly, it will set P0135” – and yes, too much time elapsed since the start and the “insufficient engine temperature data” in the ECU. So, sometimes the ECU recognises the temperature falsely.. thus I decided to change the coolant temperature sensor.

After one day the code did not set, all OBDII readiness tests remained complete. I did not give too much attention to this but it was a sign that something is not really okay: when I completed all OBD2 tests (before I changed the coolant temp. sensor) the O2 sensor test said “incomplete” after a couple of starts -> so something was intermittently bad but not always.. So, I guess this “intermittently bad” thing was the coolant temp. sensor’s signal (touching wood). The weird thing is, that I didn’t see *any* coolant temp. sensor related codes (P0115, P0116, P0117, P0118, P0119, P0125, P0128), only the P0135 O2 sensor heater related code.. every time.. so the coolant temp. sensor was not “hard down” just intermittently show bad/weird resistance. I measured the resistance of the old sensor with a digital multimeter but it is okay (in hot and cold conditions as well, soaked to hot and ice cold water) but I noticed a thin, deep green film on the sensor’s surface.

Now: monitoring.. cruising.. watching Torque displays..

Seat Toledo 1.6 16V (2001 – AZD engine code)
F-150Torqued
Member
Posts: 437
Post Re: Occasional - but avoidable P0135 (O2 heater ckt err)
on: May 7, 2015 (GMT)

@crok

Thanks for the update. It is very helpful for threads to provide hard fought positive results. And I compliment your exceptionally logical approach to diagnosis and analysis. In fact, without it you probably would still be just throwing parts at the vehicle.

I agree. Weird that the O2 heater code would result from a defective ECT sensor. Manufacturers should be required to publish the “theory of operation” for the ECU software. Who would have thought the TIME it takes for the O2 sensor heater to become ready state is dependent on coolant temperature? To diagnose some problems, you have to get into the head of the ECU programmer! Lol. But again, you took a very methodical and logical approach to the problem, and made a good choice of gauges to set up and monitor on your Torque dashboard.

Sorry I sent you on a rabbit trail a couple of times – but at least it didn’t cost too much to clean connectors and perhaps it may have averted some other future problem. We’ll never know. I would not think the green film on the sensor would cause intermittent failure.

Re-reading your update – a possibility occurs to me if the problem comes back now. Check out electrical connections / wiring in the coolant sensor wire. If you simply “unplug” the ECT sensor after “closed loop” is established, will it knock it down? Or cause your P0135 Code?

Good luck and happy Torqueing

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54371019
crok
Member
Posts: 15
Post Re: Occasional - but avoidable P0135 (O2 heater ckt err)
on: July 6, 2015 (GMT)

Hi,

So let me update the thread..

Now I have 3 weeks and 1000+km without CEL (so without P0135).

What I did in historical order:
– ECT sensor tested with disconnection: won’t cause the same
code, but a different one (P0115 – Engine Coolant Temperature
Circuit Malfunction) and

– P0135 came back..

– VAG-COM/scope testing: ECT and O2 sensor current and voltage
testing.. and the problem seems to show itself.. During the
engine operation occasionally the sensor current and voltage
showed discrepancy from normal operation – on the O2 sensor
heater circuit! I mean: sometimes the current level flowing
through the heater circuit showed 0 or near zero values..

– so I went one step further: it can happen in two cases as the
ECU is switching the circuit to ground and let the current
flow through the O2 heater element:
a, the positive wiring to the heater element has a problem or
b, the ground wiring to the heater element has a problem

– I excluded the positive wiring problem with some measurements
but it took aaaaages.. literally.. so

– I tried this “trick” with the grounding: I look up all wiring
connected to the battery’s negative terminal, the car chassis
and body.. again.. under the battery, connected to the trans-
mission.. e v e r y w i r e , l i t e r a l l y . .

– ..and you know what? It works! (Touching wood.)

Since then I did not see the small yellow sign of insanity!

Sidenote: In the meantime I had another problem as well: my EGR
valve got stuck and blocked in the upper position so all the
exhaust gases flew to the intake and the engine stall.. don’t
start.. if starts a little but there were no idle.. stalling..
et cetera.. but after an hour the engine cooled down enough and
the engine started and operated almost correctly (still no idle)
but I was able to come home and connect VAGCOM. I tested the EGR
and ran the test for 5..6 minutes. The EGR is okay now. My mec-
hanic cleaned all part of the intake system and readapted the
throttle body.. so it is okay now. Just a sidenote..

Cr0k

Seat Toledo 1.6 16V (2001 – AZD engine code)
moreause
Member
Posts: 637
Post Re: Occasional - but avoidable P0135 (O2 heater ckt err)
on: July 6, 2015 (GMT)

i was just wondering if you have an engine heater on your truck

i have heard of check engine poping out because of that

pcm check all sensor and coolant temp is not right

or coolant is high…pcm say should take a second for O2

but O2 id frozen to death lol
crok
Member
Posts: 15
Post Re: Occasional - but avoidable P0135 (O2 heater ckt err)
on: July 6, 2015 (GMT)

It’s a 1.6 16V (AZD) petrol engine, have no engine heater.

Seat Toledo 1.6 16V (2001 – AZD engine code)
F-150Torqued
Member
Posts: 437
Post Re: Occasional - but avoidable P0135 (O2 heater ckt err)
on: July 7, 2015 (GMT)

@crok

Thanks for the new update. Poor grounding is something frequently overlooked. And it can cause the MOST BIZZAR and CONFUSING symptoms. According to the wiring diagram on my F150, most sensors and actuators are connected to Battery + – and grounded by the ECU to actuate or sense. So a poor ground drives it crazy. And it is such an inexpensive thing to fix.

Congratulations and good luck.

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54371019
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