Heater Control Circuit

Hello to everybody. Im a huge tacoma fan but need some help with my car.

I want to know if anyone has come over this issue. I have a 2016 TRD Off Road M/T that has constantly 4 trouble codes coming up. P003013, P003614, P005013, P005614. They are all related to the same issue, the heater circuit.



Now, im no mechanic but I have done a lot of work to find the issue but ive had no success. This is the story behing this years long headache Ive been having.

Things to considerer:
1. I live in Honduras, Central America. Finding parts for this car isn't the easiest thing to do, and if im able to find anything, people want an arm and leg for them. I better off importing anything from the USA over here.

2: The 2016 TRD Offroad is a salvage car I bought back in November 2018. All body work was done to it and the day i took it of the shop, the Check Engine and TRAC OFF light came on the dash. Before I took it to the shop, I drove it for about 2 hours total and also refulled it during that time. No dash lights nor error codes were showing up at the time, with the exceptions for the airbag light, everything was flawless and just required body work.

3. The body work mechanic had a cheap scanner which read some oxygen sensor errors, and he tried clearing them but came right back on around 20 seconds after. He said the oxygen sensors must been clogged and suggested a full deep clean by removing all 4. I was a bit sceptical as this are relatively new cars and for what i know, the oxygen sensors on Tacoma dont fail that often let alone all 4 at once.

4. He cleaned all 4 sensors, clear the codes and the light came back on. At this points I took my car home since the body work was done and the was not making any progress with the error lights. I decided to diagnose it myself.

5. I started by checking all the relays and fuses from the engine bay and drivers kick panel, they were all working fine and now issues were found there. At this point I knew I was doing some sort of scanner, I went on ebay and bought the a Mini VCI cable and downloaded techstream.

6. I cleared all the history on the codes and ran a scan, in which the codes P003013 and P005013 came up and a minute later codes P003614 and P005614 showed up. With abosolutely no luck whatsoever on locating the issue, I decided to continue with my life and let the car sit from January 2019 to around now. I drove it occasionally, but mostly left it in the garage.

7. Last year I also bought a second Tacoma, a 2017 TRD Sport 3.5 V6. Since they had the same engine I decided to swap the 4 sensors from one to the other. I switched the 2016 sensors to the 2017 and the 2017 to the 2016. Surprise, the 2017 TRD Sport did not show up with any error from the sensors and they were working perfectly find. On the other hand, the 2016 Off Road had the 2017 sensors and still the exact same codes came up after clearing all of them with techstream. Here I was certain that the sensors were not the issue and it had to be some type of electrical malfunction.

8. I started playing with the relays once more and swithed ALL the relays from the 2017 to the 2016 and also vice versa. Once more, the error codes only showed up on the 2016 and the 2017 was running like a champ.

9. Next I figured it had to be some sort of ground point issue, so I checked 4 ground points that i was able to located, 2 on the engine bay and the other 2 on the cabin. The first one was the one right by the engine fuse box, i cleaned it and made sure it was making good contact as the body shop had repainted the fender and also sprayed a layer of anti corrosion paint on parts of the engine bay to prevent rust. No luck with that ground points so i move to the second one behing the windshield wipers reservoir, cleaned it and ensure good contact, still no luck. I moved to the ground points on the cabin, 1 in the drive kick panel and 1 on the passenger kick panel. Those were showing up perfectly fine and just ensure there was good contact on them.

10. I figured that if the cabin ground points werent properly attached, I would have a christmas tree on my dash, not just the check engine with trac off light. So once more a said "Screw this" and kept my 2017 as my preferred Tacoma.

11. Last thing I did was yesturday when I tried the "Learning Value Reset" option on Techstream, but to be sincere, im not sure how that actually works. I just clear the codes, ran the option on techstream and then took it for a quick drive. The lights still came on and didnt go away. I talked about coolant temp being 176 degress for the learing process to start, I took a look on the data from techstream and it was showing a temp of 190. So Im pretty sure it did its thing, if anything was suppose to be done.

So this is all the things I have done to my car. I have recently gotten to work on it once more as the corona virus outbreak has left me shutdown from work and the local goverment has placed quarantine. I have MORE than enough time to meticulously check everything from scratch once again but Im desperate for help.

Resorces used:
Tacoma 2016+ Repair Manual
Wiring Diagrams
Some 2017 Tacoma Sport parts
Toyota Techstream Software

Something that have clicked on my mind are:
1. Is there any additional ground points that i need to check?
2. I followed the wiring diagrams, but Im not an expert in reading them. I get lost on some connector junction and could this be the reason i might be failing?
3. Can relays be swithed from place to place?
4. Any option on Techstream that can give me a clue on how to fix this?

Any help will be highly appreciated. Thank you all for the support and great ideas provided in this forum. You have all provide great ideas for mods in my Tacomas.

 

It's the heater circuit in the sensor. Ohm across the two pins that go to the sensor and back to the plug, I bet you'll find it open.

Its just a resistor heating element to warm the sensor before the truck's exhaust has been able to.

If it's open, change the sensor. Easy as that. Compare to the other sensors.

Edit, hold on, I'm an idiot and didn't fully read, but I'll leave above for other people's reference in future searches.

It gets more complicated here but you need to see what all of those things share. Possibly the same power supply, a bad sensor or damaged/shorted harness could have popped the fuse and killed all 4, does the power supply go to a splice before the sensors, is there a connection that wasn't seated or a pin bent during after the repair?

What about it was damaged to warrant the salvage title?

On the cars I work on, the control circuit goes from the ecm to the power distribution module, so it's a relay control wire, the ecm provides switched ground (to close the relay) when it wants to turn the heaters on. It monitors the circuit by reading if there's voltage on the wire its controlling. If it sees voltage, that means there wire from the fuse to the relay and to the ecm are all OK. Its really backward sounding but its makes sense and is an easy way to monitor a circuit.

 

Im reading all the diagrams and the heated senesors are linked to the Efi no.3 Relay and also the Engine Control Module. There is something else thats called VSV (Purge) with i have no clue what it is.

What about it was damaged to warrant the salvage title?
Well, I actually dont think so as i drove it before i took it to the shop and no lights showed up. I even refilled it with gas and no errors were showing. My main guess is that the body shop disconnected something or pulled on some connector which has a loose wire or some sort of loose ground

 

Could you post the diagram you're looking at? That would be a huge help for me in trying to help you.

Was it a flood vehicle, where did it get hit, etc?

Oh yeah, re: #2
Only on cold-starts will it need to turn the o2 sensor heaters on, so it may seem intermittent but isn't.

 

I was hit right on the right fender and the right side of the bed, nothing too major compared to some i seen. Its mostly just big body parts that were replaced, no frame damage at all

 

Both downstream sensors share the same power from the same splice and the controls both to through IH1 before making it back to the ecm... (I'm still looking at the diagram)

Yeah, I see the upstreams get power from a splice of sorts at the AF HTR relay...

Screw looking at this on my phone, let me grab the laptop...

https://drive.google.com/open?id=1cx5nnlnCzlhI45D1vbBMj1ni983SKdKf
page 2986 shows what readings you should have at the sensor connectors back into the truck, so to speak. See what's not right on all 4 and trace back to what they share.

My 3 year old son is crawling all over me wanting me to play (as he certainly deserves), I'll check back in a while to see what you've come up with.

 

I surely understand and no worries, as I said, I have all the time in the world right now. I'm going to check those lines and be back with a update. Might get back with you a little late as I also have to run a couple of errands.

Thanks so much for the support

 

Ive been trying to follow that diagram but get lost since im not real good at this. I really have to beg you to please bear with me with some questions I have.

1. Im tryin to find the IH1, now is that inside or outside the car? My guess is outside as the likes that show "shielded" must be going trough the cabins firewall. Right? If not, then what does "shielded" line mean?

2. Are the octagons found in the circuit some sort of conectors or wired that are join together?

3. That EA1 line, were is that in the car possibly? Im trying to follow the cables but i loose most of them in the harness that goes from the heating sensors to the top of the transmisson and then to the back of the engine.

I checked all sensors, I unplugged them and checked the values to the sensor itself.

Both Heated oxygen sensors were showing 7 to 8 Ohms on the pins 1 and 2
Both Heated oxygens sensors were not reading anything on pints 1 and 4

Both Air Fuel Ratio Sensors were showing 2.5 to 2.7 Ohms on pins 1 and 2
Both Air Fuel Ratio Sensors were not reading anything on pins 1 and 4

Im not sure if im doing something wrong when checking the sensors, according to the manual pin 1 and 4 should always have at leats 10 Ohms. I also went ahead and checked my 2017 tacomas Heated oxygen sensors, and those were also showing the same pattern, 6 to 8 on pins 1 and 2. And no readings for pin 1 and 4.

 

Outstanding post. This is the first time I've heard anyone use the word "Ohm" in a reply. You should do a thread about the 99 other things you do before you throw a part at a car..lol. Matrix? What the hell is a matrix? Just buy a new sensor and you're good. Lol. Thank you for giving me hope. Great diag.
Zim

 

You're doing great! You checked what you have, compared to it's mate and compared to a known-good part. You seem to have your head on straight that's why I'm trying to help!

I'll answer questions first.

1.1: I have no idea where IH1 is, I haven't found anything to layout where connector locations are yet, I've just haven't found the resource for that yet. I'm new to Tacomas, just got mine at Christmas, lol
1.2: shielded means, in this and most cases, that they are wrapped in foil and/or woven metal strands that go to ground on one end or another. It serves to absorb electromagnetic interference and zap it to ground. In this case, it's to keep interference out of the circuit and keep a clean signal to the ecm. Maybe the harness drapes over or runs along the alternator's cable or something, maybe just good insurance, I dunno. Sometimes a cable will be shielded to keep interference IN. Like on a 3-phase low pressure fuel pump, it'll usually be shielded from the controller to the pump but it's to keep the voodoo in, not out. And no, doesn't necessarily have to have anything to do with the cabin per se.

2: to me, the octagon would appear to be a splice where all the wires come together and are bound and insulated. In my world its a sonic weld and a butyl cap thats taped up in the harness. A Toyota tech could tell you what exactly you'd be looking for.

3: EA1... see 1.1 lol, sorry man, I just don't know yet.

Now check in the opposite direction, meaning into the truck side of the harness. KOEO (ign on, engine off), Meter on ohms, black lead to body ground, read all 4 pins on any two sensor connectors. Ground will read, well, ground (clean, low ohms), power if present will probably be battery voltage¹ (not a filtered 12.00v or 5v) and your signal wires should read Megaohms or Kilohms to ground.²

You should not have a clean ground, iirc its a ground-switched heater. The ecm gives it ground to heat the sensor. That should read open if the engine is warm and should read ground (closing the heater circuit) if the truck is trying to heat the sensor, if the truck hasn't run today, it may well be trying to heat them.

Here's some quality logic that I learned on my own. Soak this in:
¹ If you didn't read power on a sensor when you were expecting it and since they share a spliced power, the next step would be to ohm from one sensor connector to another. Both downstreams (B1S2, B2S2) share power, yeah? So ohm from what should be b+ on one sensor's connector to the other. If good, then you know your wires are good from the sensor to and through the splice back to the other sensor. If good and other things that get power from that splice aren't failing, it's most likely not that even if you were expecting power on the circuit and didn't have it. Yeah, I learned that the hard way, lol.
² if you're checking communication/signal wire from the user/consumer/sensor side of something back to a module, or even on the CAN between two modules, you can read continuity to ground on each signal wire and you should read kohm or Mohm. What you're reading is ground through the circuitry of the module and it means your wire makes it to the module intact, no need to dig around about it and don't bother ohming end-to-end on that wire, you just did, effectively. Not a cheat, it's using logic. Warning, that only works on a single wire signal wire. If it's a spliced LIN-bus, its like the shared power example above.

Kinda got myself swirled around there, the Concerta hasn't started working yet

Let me know what you find reading into the truck side and I'll check it out later. Now I'm going to nuts putting speakers in my truck. Focal component front, coax rear, LC6i, kicker key 4ch, kicker key 500.1, loaded kicker 8" L7. Might make a thread on that later? Not sure.

Afternoon edit: make super positive every ground that goes ecm to body and engine harness to engine block/head and, if applicable, the transmission harness is good. Actually make sure they are tight. I know you said you did, at least reinspect in the areas of repair, along the cowl, anywhere they would have taped a spray line, etc.

 

Well hot damn, look at those splices right in the open by my battery. White/black are ground, look down in the tape... I see at least one, maybe two blue splices. Looks an awful lot like your octagon above and its right where you truck got hit. Have fun digging, thats definitely where I'd go before going back to the meter!

 

I found the IH1 connectors, its located behind the glove box next to the 4WD module. After spending hours studying the diagrams, I finally managed to know to read them and how to find the exact pins from the connectors. I also believe the splice (Octagon) that deliver power to the sensors from the 10A fuse is located right on top of the transmission. I couldn’t get my hand up there but I’m also 100% positive that it’s there. No with that said, I measured the voltage on the junction’s connectors from the heater sensors and when were only showing about 3v – 5v with the engine running.


I also removed the sensors from the pipe line and put 12v on pins to ensure the heater circuit was working properly, it took around 4 minutes and it reached a high temp, don’t know exactly how much since I don’t have any temp meter, but it was too hot for the touch. Both sensors were heating up properly so I reinstalled them.


After all that I check the continuity for all the lines to the sensor directly. I first tested the 10A fuse from the engine box to pins in the connector, they all followed through properly. I also checked continuity from junction IH1 to pin1, it also was working following through properly. Last I checked the continuity from the ECM (Connector E11) to the sensor, and it also was following through properly.


At this point I started to check all over for the “shielded” lines, but no I couldn’t find anything. Its supposedly a gray connector that should have a white, brown, brown, brown and white cables in the first 5 pins. I looked in the passenger kick panel, passenger kick panel and even the engine bay, but nothing.


I’m giving all this another shot tomorrow as I’m starting to get frustrated working sections of my day to achieve no success. I was trying to do this by myself as I have all the required tools but am missing the knowledge! I’m soooo close to say screw this and take it to an electrical shop but my shallow pockets and quarantine have me doing this myself. I won’t deny that I actually really enjoy this type of actives and love learning new things, specially having to do with cars, every day.

That is actually the first ground point I checked before I started to take anything apart. What I did was unscrewed it, turn the ignition on, and a whole Christmas tree lit up on the dash. I took 150 grit sandpaper and left the bare mete to make sure everything made proper contact. Same procedure was made to another ground point I located right next to the air box, but still no luck on them. Im doing to check those ground points once more tomorrow including the 2 ground points on the driver and passenger kick panel.

 

I'm sure taking the ground loose pissed everything off, lol

Did you take a good look at the blue splices shown as well?

Check out page 3969 in the manual I posted.

Between the quarantine and it not causing a driveability issue, if you're tired of fooling with it, take a few days and look at it later. Sometimes that's what you have to do. No worries man.

 

I had these codes after I cut my O2 sensor wire. Replaced it and still had them...swear I checked all my fuses but dealer told me all they did was replace a fuse in the engine bay. I would triple check them all again.

 

Did you guys manage to figure out the issue, i have a 2020 Tacoma with the same problem.

 

Might be a long shot but are the fuses in the correct locations? I ran into that on a civic once.. it was a heater code and figured out that someone misplaced a fuse and put it in a different spot. Threw me for a loop for a little while. Just something to double check.

 

Hello there...
Dude Reading through your post felt exactly like my day, I couldn't have written my problem the way you did.

I had the same thing with my car, it drove me crazy. I did every thing as per the manual. All the reading were in perfect match with the factory settings. Still that fault never went away.
I finally decided to order brand new four sensors hoping the issue will be cleared.
To my surprise the fault code never went even after replacement of all sensors.

Upon further investigations and inspections I found a lose ground wire that connect to power steering pump (vane pump). Luckily I connected it and the fault disappeared immediately. Went back to the old oxy sensors and everything was fine.

Don't ask me about the link between the two - oxy sensors and steering pump ground wire- though.


Check your car hopefully it's the same issue.