NEED HELP BAD-NO CODES, CEL-on, Rough Idle, Hard to Crank

Well I do have some evidence of rodents, below the intake manifold there is half chewed acorns, and Mr jingles had a nice little house built in my Air box a couple years ago. So I will check into all the wiring behind the dash/glove box the best I can get to. Went and bought an inspection camera today I was already going to buy, that will definitely come in handy. I really do appreciate all the input everyone is giving me here. I'm so deep in this little truck now that I feel like I'm in no mans land. I might also (if the visual inspection doesn't reveal anything) Disconnect and jumper the poss and neg clamps for 24 hours then re-attach and see if that makes any difference.

On another note, blue driver support is sending me another scanner to see if its my scanner not picking up, life would be soo much better with a code that I could actually chase down.

 

hope you find something!

IMO the good news is fairly non-expensive fix

unless you want/need to RR the eaten harness(s)
again, electrical Guru's will have better opinion whether the electronic 'signal' might be too delicate to repair harness wire(s)

 

i would like to reach out and ask if anybody knows where ALL the grounds are on this truck. I have found 6 total, under the hood- By the fuse box on the frame, one the intake manifold on the drivers side, on the passenger side on the frame by the cruse control module, on the frame behind the engine (this one attaches to the back of the engine then to the frame). Inside the cab- One behind and a little above both driver side and passenger side kick plates. That's all the grounds I have been able to find, some models look like they had a ground attached to the underside of the back of the bed right behind the back bumper. I have a spot for a screw but no wire and no screw. Just wanted to double check to make sure I'm not missing any...

 

OP,
As pointed out previously, the (F) type female connector on a sensor can break down with age and become brittle which can compromise the connection. Further, water is kept out of the female connector by small rubber-like plugs around each individual wire going into the female connector. Our joint 1st Gen Taco problem is that these small plugs shrink with age, so the original plugs no longer keep water out of the female connector/connection. These OEM (F) type female connectors for the Camshaft/Crankshaft/Oil Pressure/Coolant Temp sensors on our 3.4L V6 are available. When I change a sensor on my '97 3.4L V6 Taco 4x4, I also change the (F) type female connector. Am waiting on an OEM

$29 89422-35010 Water Temperature Sensor

89422-35010 Coolant Temp Sensor and the OEM 90980-11062 female connector now. Unfortunately, I am chasing down an intermittent problem which is eerily similar to yours. If this new OEM CTS and connector does not solve my intermittent problem, I will be beating my head against the wall same as you. Both our problems may be something small that we are overlooking such as corrosion causing a poor, erratic connection to a sensor or a failed vacuum line. I am of this opinion because corrosion in the female connector/wiring has already caused my Cam Pos Sensor to send erratic signals to the ECM. A split vacuum line leading to the fuel pressure regulator that was not immediately visible also caused almost the same situation as you are dealing with now. So be sure to check the little things that can bite you in the ass so hard that you overthink it and start replacing serviceable parts. I am guilty of that myself, especially on older vehicles that have been neglected. Best of luck with this headache!

As far as grounds go, I felt that adding a ground from the engine to the frame in addition to upgrading all the other ground wires was a good idea. Cable kits are available to replace/upgrade wiring, but I prefer to use marine grade tinned copper wire cables custom made by batterycablesusa.com. You save money and get better cables than I have seen in the premium "Big 7" kits.

'97 3.4L V6 Taco sensor (F) type female connectors: These OEM Toyota female connectors come from Toyota without the rubber-like plugs/internal pin connectors.

Camshaft Position/Crankshaft Position: 90980-10947
Oil Pressure:

$13 90980-11363 1x Connector 1-way 1 pin for Toyota Oil Pressure Sensor 90980-11363

90980-11363
Coolant Temp: 90980-11062
Coolant Temp Sensor wire complete with both connectors ($8):

$18 82219-34020 Sensor Wire

82219-34020

 

Checked and rechecked that connector, I might just go ahead and replace it anyway. The Fuel Pressure Regulator hoses are good. BUT I FINALLY GOT A CODE. Weird but I put the scanner in and was just checking to see if if would give me something and it popped up with a P1600 ECM Batt Malfunction...... Any tips with that???

 

So per the service manual, I checked the 15 amp EFI fuse, it was good, I then went and checked the voltage between terminal BATT of ECM connector and body ground and was reading 13.01 volts which is in the acceptable range of 9-14v, now I'm trying to measure the resistance between the ECU ground terminal and the body ground from IN-29 in the service manual. Does anyone know where this is? I have attached pictures of the service manual that shows the connector and then I have included a picture of what my ECU connections look like, these don't look like the same connectors....

 

ALRIGHT. So this is where I'm at now. I tried doing research on what the ground terminals are on my ECU, a couple of things were pointing to the E1, and E2 which in my case are (if your looking at the picture of my ECU above) Are located at E8 then terminals 13 and 26. So I ohm'd those out with the other lead against the body, and was reading 160+ on each. This is with my meter set to 200. So I thought that's weird, I went under the hood and tested each ground and it either wasn't reading anything or maybe .1 . So I disconnected all the grounds that were attached to the intake manifold and found the single wire to be a good reading, but the pairs were showing the 160+, so I separated those and it is the left hand side if your looking at the two pairs that is giving me this reading (See Pics). So, again I'm not a mechanic but my next step would be to trace down those two wires and they are bad somewhere right?

 

code P1600

 

Can anyone confirm the wires I need to back test on the ECU are in connector E8 terminals 13 and 26 if I’m trying to test the grounds on the ECU? If so, if I have high ohms would this point to a break/bad connection in those wires if I test each to the body and get a reading of 160 ish when my meter is set to 200 ohms? Thanks.

 

Still nothing....

First I want to say thank you for everyone that has contributed on this, I really do appreciate it. I have spent the last two days on this truck to no avail.. This is where I'm at.

Checked the ground wires that attach to the intake manifold then to the ECM E8 connector and terminals 13 and 26, both are reading 0.0 Ohm. Sorry about the post with the meter pics, I know some mechanics out there are shaking their heads, the ground that I was using at the time to test those two wires going to the ECU was not a good one. Once I got on a good ground those wires are reading good. I took the wrap off the wiring harness before I found this out.....The wires look good though..

So I have voltage to the ECM in the Acceptable range, and it appears I have good grounds. In Controlcar's post it talks about the battery or the alternator not properly charging the battery. I just replaced the battery, have not checked to see if the alternator is functioning properly (not sure if I should even check this at this point, because of the new battery). At this point I'm thinking it might be a bad ECU (Controlcar). The FSM talks about checking the connector on the harness for contact pressure. Any advise on that? (leid) I did check and double check the connector going to the ECT sensor it appears ok, nothing that would strike me as causing a problem, but I'm going to go ahead an order that little connector just in case. Thanks.

 

The OEM 90980-11062 ECT connector from Toyota is just the outer female F connector itself without the rubber-like plugs/internal pin connectors. Ordering the OEM 82219-34020 complete wire including both connectors is the way to go IMO. I have one on order now. This KSV Looms "OEM" 90980-11062 ECT connector sold on Amazon & Ebay comes with the outer female connector/rubber-like plugs/internal pin connectors (below). It will work, but I am not convinced of it all being genuine OEM Toyota/Lexus parts.

KSV Looms 2-Pin Connector Kit for Toyota Lexus 90980-11062 Water Temp Sensor Plug Clip

Amazon.com: KSV Looms 2-Pin Connector Kit for Toyota Lexus 90980-11062 Water Temp Sensor Plug Clip : Automotive.

 

It's be a bit since I have had time to work on my truck any. I figured a little rest from it was good. Started putting everything back together again today and decided to wrap all my wires in the HONDA rat tape, so that maybe I wont have problems in the future with mice. I went ahead and pulled the ECU to check it, it's about the only thing left I haven't replaced, I took the cover off and I believe this has been my problem. You can clearly see an issue at one part of the control board. I'm now in search for a 89661-04310 ECU. I have checked on some of the 1st Gen Tacoma parts forums, but don't know how to search for this specific number on there. Anybody have one of these they would part with?

I also would like to take a second and say thank you for everyone that contributed to trying to help me and I'm very sorry if I was a bother to the real mechanics out there. Just a guy trying to get his dream truck up and going... Thanks again for everything. I will try to update one more time if this fixes my truck with some pics..
s,

Jason

 

there is no applogy necessary. I will add this to the list of things to check in the future. It isnt hard to pull the PCM and take the cover off for a look see and this could save a lot of diagnosis time. In most factory diagnostic pin point tests there is always a final line that says replace with known good unit.

 

I’m so glad you found a potential resolution
And
Thanks a bunch for the update!!!!!

someone posted a highly recommended/reputable ECM/PCM rebuilder a while ago
Lemme find

 

If u can’t source…….
Would be worth a shot


https://www.unitedradio.com/

 

OP,
My intermittent problem was an intermittent O2 sensor even after both original OEM O2 sensors tested as serviceable. I replaced both sensors with aftermarket DENSO O2 sensors from RockAuto after seeing the fuel system go OL (Open Loop) for a split second (CEL momentarily illuminated but no code) at warm-idle then back to CL (Closed Loop), which screamed bad O2 sensor to me. Most probably the upstream sensor was intermittent, but I replaced both sensors as a shotgun remedy. After replacing both O2 sensors, my Taco is back running like a champ. Just because a sensor passes an Ohm test does not mean it is not causing an intermittent problem. Best of luck with your problem if it has not already been solved. Bottom line: This is the 2nd time in 28 years of wrenching my own Toyotas that I have had a hard-to-diagnose intermittent problem with no codes on a Toyota and the 2nd time it has been an intermittent O2 sensor. From now on, an intermittent O2 sensor goes to the top of the suspect list for any intermittent sensor problem I have.