CELs love me

[Mudeprived]

I haven't had a month go by without a CEL on both my jeep and 4runner. It's a streak I would LOVE to end. I solved the jeep crap but now I'm dealing with the 4runner and could use some help along with my research.

In august I had a few codes pop up:

P0125
P1130
P1135
P1135p

I replaced both sensors on my Cali exhaust with Denso sensors. The CEL has been off for a couple weeks. Today it came back on with three codes but with a P at the end.

P0125
P1130p
P1135p

So I thought the sensors would eliminate the code but I guess something else is going on.

Can anyone chime in with their suggestions on what to do next?

Thanks

1999
Limited
157k

 

[snow junky]

O2 codes are Probably from defective sensor ban connection or melted wires

For the p0125 code. What does the readers engine coolant temp see? If it’s accurate then your thermostat might be stuck open. I would get that figured out before replacing o2 sensors too


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[Mudeprived]

O2 codes are Probably from defective sensor ban connection or melted wires

For the p0125 code. What does the readers engine coolant temp see? If it’s accurate then your thermostat might be stuck open. I would get that figured out before replacing o2 sensors too


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FYI the sensor worked fine for the past 1000 miles or so. The wires were zip tied away from the exhaust. I will check the wires again.

What do you mean by "readers engine coolant temp see"? If you are speaking of my code reader then it has no reading. It is a basic OBDII reader from HF.

Edit: I almost forgot about the sensor. I received DENSO 234-9001 instead of 234-9002. I read that the only difference is the wire length? Is this correct? Could this be an issue?

 

[octanejunkie]

Both P1135 and P0125 codes are are related to the closed loop operation (coolant temp) and the Air/Fuel (upstream) sensor in the CA Exhaust system. The post-cat (downstream) sensor is an O2 sensor.
https://www.obd-codes.com/forums/viewtopic.php?t=6724

The codes you are getting imply that the coolant temp sensor is not reading the right temp and not allowing the ECU to enter closed loop mode. Check our thermostat and coolant temp sensors. Your thermostat may be stuck open; that would be the easiest fix.

The other implication is that the A/F sensor is not getting up to temperature (1200 degrees F) fast enough, which may be a ECU timeout issue due to the first issue, insufficient coolant temp forcing vehicle to stay in open loop mode.

If you address the coolant temp issue but the other code persists, check the wiring at the sensor connection to make sure you are getting voltage and resistance as required and there isn't a short in the harness pre-sensor. Hopefully someone with a FSM and circuit diagram can chime in with the correct values and pinout of the connectors.

Since you already replaced the AF sensor, I would focus on the thermostat and coolant temp sensor, in that order.

The risk of driving with these codes includes ruining the cat, so be careful, those are more expensive than any of the parts implicated here.

Good luck, brother

 

[snow junky]

FYI the sensor worked fine for the past 1000 miles or so. The wires were zip tied away from the exhaust. I will check the wires again.



What do you mean by "readers engine coolant temp see"? If you are speaking of my code reader then it has no reading. It is a basic OBDII reader from HF.



Edit: I almost forgot about the sensor. I received DENSO 234-9001 instead of 234-9002. I read that the only difference is the wire length? Is this correct? Could this be an issue?

I’m not sure about the sensor. Most are universal 4wire sensors.

Yea I was talking about the scanner. Some better ones will give you real time data. If you have a multi meter you could bench test the coolant temp sensor.


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[nc-grayson]

Love this forum. Yesterday I experienced literally all of these codes out of thin air. Non-Cali spec, oem thermostat replaced 5k ago. Definitely riding around stuck in OPEN loop...yay horrible mpg'. ScanGauge reads proper coolant temps of 188-190, so I assume my coolant temp sensor is doing fine, as well as the thermostat not being stuck open.

Guess it's time for some new 02/AF sensors! 185k...they had a good life.

 

[4Reak Show]

See it a lot on highlanders mostly but A/F sensor not warming up or changing quickly enough sets a false coolant temp code. Make sure your vehicle uses an A/F vs 02 in front. Easily deciphered with under hood smog lable (if your hood is original). Says something like EVAP, SFI, TWC, [and then either H02S(2) or AFS, H02S: indicating either 2 02's or one and one].

Seen a few on 4 cylinder Tacomas do it too. Customer gets a free Autozone code scan and has us toss in a temp sensor with no change. AF sensor fixes it everytime. Probably done about 15-20 Toyotas.

And yes, I believe a 02 will plug in place of an AFS. Best to go to dealer and go by vin for 100% accuracy. Good luck.

4Reak

 

[Mudeprived]

See it a lot on highlanders mostly but A/F sensor not warming up or changing quickly enough sets a false coolant temp code. Make sure your vehicle uses an A/F vs 02 in front. Easily deciphered with under hood smog lable (if your hood is original). Says something like EVAP, SFI, TWC, [and then either H02S(2) or AFS, H02S: indicating either 2 02's or one and one].

Seen a few on 4 cylinder Tacomas do it too. Customer gets a free Autozone code scan and has us toss in a temp sensor with no change. AF sensor fixes it everytime. Probably done about 15-20 Toyotas.

And yes, I believe a 02 will plug in place of an AFS. Best to go to dealer and go by vin for 100% accuracy. Good luck.

4Reak

This is the mistake I almost made initially but then got a AFS sensor.

 

[octanejunkie]

This is the one I got
Denso 234-9002 Air Fuel Ratio Sensor https://www.amazon.com/dp/B000C5YCYS/ref=cm_sw_r_sms_apa_Q-NZzbE7JX5S5

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[nc-grayson]

O2 codes are Probably from defective sensor ban connection or melted wires

For the p0125 code. What does the readers engine coolant temp see? If it’s accurate then your thermostat might be stuck open. I would get that figured out before replacing o2 sensors too


Sent from my iPhone using Tapatalk

so wait....it's late and I'm tired....and now i'm confused that I read this the second time.

you're telling me that if my SG reads normal coolant temps of 188-190, then my thermostat might be stuck open? If it was stuck open....wouldn't it be running cool? Help me wrap my head around this?

 

[octanejunkie]

so wait....it's late and I'm tired....and now i'm confused that I read this the second time.

you're telling me that if my SG reads normal coolant temps of 188-190, then my thermostat might be stuck open? If it was stuck open....wouldn't it be running cool? Help me wrap my head around this?

Stuck open means it takes longer to warm up and stays in open loop

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[snow junky]

so wait....it's late and I'm tired....and now i'm confused that I read this the second time.



you're telling me that if my SG reads normal coolant temps of 188-190, then my thermostat might be stuck open? If it was stuck open....wouldn't it be running cool? Help me wrap my head around this?

stuck open may never even worm up if there is enough air flow through the radiator.

The reading you got was most likely after running for a bit and at a stop.

Stuck open tstat may not even be your problem but I defiantly wouldn’t rule it out because of normal operating temp readings.

 

[nc-grayson]

Stuck open means it takes longer to warm up and stays in open loop

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stuck open may never even worm up if there is enough air flow through the radiator.

The reading you got was most likely after running for a bit and at a stop.

Stuck open tstat may not even be your problem but I defiantly wouldn’t rule it out because of normal operating temp readings.

thanks fellas. I guess my questions is, " would my SG still show 188-190 temps if the thermostat were stuck open?"

 

[Mudeprived]

I don't know if this helps but I noticed a very strong exhaust smell when idling or backing up into my car port. I am not familiar with the terminology for it "smells like it's running rich" or something like that but I figured it might help diagnose it.

I have an OEM thermostat on it's way.

 

[Mudeprived]

Ok here is another update. I reset the codes and drove it to the bank and got only the P0125.

I reset it again then drove 19 miles and the CEL pops on again with P0125, P1130, P1133, P1135. This was after it was already at operating temps.

Does this tell anything?

 

[TheDurk]

Both P1135 and P0125 codes are are related to the closed loop operation (coolant temp) and the Air/Fuel (upstream) sensor in the CA Exhaust system. The post-cat (downstream) sensor is an O2 sensor.
https://www.obd-codes.com/forums/viewtopic.php?t=6724

The codes you are getting imply that the coolant temp sensor is not reading the right temp and not allowing the ECU to enter closed loop mode. Check our thermostat and coolant temp sensors. Your thermostat may be stuck open; that would be the easiest fix.

The other implication is that the A/F sensor is not getting up to temperature (1200 degrees F) fast enough, which may be a ECU timeout issue due to the first issue, insufficient coolant temp forcing vehicle to stay in open loop mode.

If you address the coolant temp issue but the other code persists, check the wiring at the sensor connection to make sure you are getting voltage and resistance as required and there isn't a short in the harness pre-sensor. Hopefully someone with a FSM and circuit diagram can chime in with the correct values and pinout of the connectors.

Since you already replaced the AF sensor, I would focus on the thermostat and coolant temp sensor, in that order.

The risk of driving with these codes includes ruining the cat, so be careful, those are more expensive than any of the parts implicated here.

Good luck, brother

Gonna disagree here. It's not the temp sensor. Ignore the silly P0125 as long as you have a P1135. P1135 is bad front A/F sensor heater or heater circuit. That means the ECU can't make sense of the temp readings because they don't jive with the o2 readings. FSM says this in Toyota speak. Focus on P1135 first as it is unambiguous code.

Check the resistance in the sensor heater. If open or short, you got a short-lived sensor. If nominal (At 20°C ( 68°F) 0.8 - 1.4 Ω), then you likely have a connection issue. Check plug and connector carefully and clean with contact cleaner. Then check wiring as much as you can see along the underside. Turn key on and check connector voltage to the heater--one side should show ground and the other 9-14V+. If good, reset and see if you fixed it. Fix that P1135 and all the rest should fade away.

Never seen the trailing p on any of the scanners I have used--and that is a lot going back to 1996. Can't help you on that.

 

[octanejunkie]

I knew someone would have the values to check on the AF sensor wiring. Thanks [MENTION=10169]TheDurk[/MENTION] [emoji1360]

Perhaps the trailing p is a pending code on OPs meter; otherwise I've never seen that either.

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[Mudeprived]

Thanks for all the excellent information. I got a question about using my multi meter. I have a standard cheap red one and wondering what to set the knob to when testing the sensor?

 

[octanejunkie]

Thanks for all the excellent information. I got a question about using my multi meter. I have a standard cheap red one and wondering what to set the knob to when testing the sensor?

There should be a few settings, AC, DC resistance, etc.

For voltage you want DC. For sensors, usually resistance [emoji755] (ohm symbol) unless you are measuring sensor voltage.

Post a pic of your meter.

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[Mudeprived]

https://www.amazon.com/Neiko-40508-...F8&qid=1506891644&sr=8-10&keywords=multimeter

That's what I have but red.

I tested my old factory sensor on both black wires and no resistance. I tested my old 02 and it still was functioning. So I went outside and tested the 600 mile sensor and it's dead. No resistance.

DENSO 234-9002 Air- Fuel Ratio Sensor-OE Style Air/Fuel Ratio Sensor - Up-stream

That's what I bought. Open box item. I took my chances but should've done what I preach and done it right the first time. (rolling eyes).

update: I kinda got my $$ back in a way. Amazon has it for $114 and I got $50 off by applying for their Credit Card. $64 shipped. I will just cancel the credit card when I get it.