Looking for Engine compartment harness to under dash harness connector pinouts.

Long story made not so short, a wire smoked...insulation burned off and melted many other wires in the engine wiring harness, which includes the engine fuse box, and the firewall pentation. There was also wires damaged from the kick panel connectors and the under dash harness, but it was very limited.

About 30 hours of labor later, I have repaired all the damaged wiring...I think. That included separating all the wire from the silicone firewall plug. Now everything is bundled back up and everything reinstalled. The truck runs again, but...

I have a code for the thermostat heater, which sets the Check Engine light and disables the cruise control and limited slip.

I have replaced the thermostat housing, because it is easy to get to. Now I need to trace the one wire, without pulling the fuse box and firewall penetration apart. If its not a wiring problem, then it means that output from the ECM got smoked and I need a new one. $$$

Anyone have a source for the pinout of all the connectors in that drivers side kick-panel? I need to trace from the ECM to that kick panel connectors and back to the thermostat. I have wiring diagrams, but they do not show the connectors behind the kick panel. The wire is BLACK and there are multiple black wires in that harness.

Thanks in advance.

Edit:
More tracing and there is are several connectors in the engine compartment fuse boxe where it may change colors also.

 

Toyota does not provide pinouts for harness joining connectors, in any case there is no intermediate connector between the control wire at the PCM and the thermostat heater.

The thermostat heater get's supplied battery voltage on Pin 1 (Blue) from the EFI No 3 Fuse (!0A), the PCM Controls the ground on Pin 2 (Black).

Easy enough to test the circuit with a test light, make sure you have power at Pin 1 of the thermostat heater with the key on.

If you have a bi-directional scanner you should be able to put a test light across the terminals at the thermostat heater, command the thermostat heater on, and see if the light lights up.

Which code(s) are you getting?

 

Agree, there are no intermediate connectors from ECU. There could be a connector from the sensor to the harness. Test the battery power on the ping, if the power is missing, run a wire via add-a-fuse to the pin and see if takes care of the issue.

 

Thanks for the prompt replies folks!

I've got 12 volts on the + pin at the thermostat housing connector. I was trying to test at the firewall connectors and avoid pulling the right side dash apart (again), but I will do that this morning so I can test all the way to the ECM connector.

The drawings I have are like the ones provided above...they do not indicate a intermediate connector. This is puzzling. If there are no intermediate connectors between the Thermostat housing and the ECM, then the wire in question must route through the firewall on the right passenger side. The left driver side harness is where the damage was located and I know that all wires penetratingly there go through at least one intermediate connector. There are also a set of intermediate connectors in the engine compartment fuse box and I suspect this wire routes through one of those also.

 

I mean if it doesn't show it going through an intermediate connector on the diagram then it doesn't unless there's a typo on the diagram but from what I've seen most of the engine and transmission wiring on Toyota's goes directly to the PCM without going through an intermediate connector.

Majority of the stuff going through the intermediate and junction connectors is body/chassis stuff, powers, grounds, and things that go to multiple modules.

 

Which code do you get?
you need to check the resistance between pin 2 on the connector for the heater and ECM pin 22 (there are not any connectors in between).


If within the range, you need ECM.

Looks like you already checked pin 1 to the body ground. But here is the procedure just in case.
Did you replace with OEM inlet or aftermarket?

 

BTW, ECU for your year is about 120-200 for used.
Part # 89661-04k53

 

Thanks for all the help.


The code is P0598 - Thermostat heater control circuit low.

I pulled the glove box and unplugged the EMC connecters and tested there. No short to ground and good continuity all the way to the connector at the thermostat housing connector. The thermostat connector also has good 12+ to the other terminal of the thermostat housing connector when the key is on.

That leaves the ECM.

Does that ECM have to be programmed to match the VIN? I has seen some references to that, but it was not clear on what years and modes.
I love to be able to pick up a used one.

 

Yes and will require a reset of the immobilizer. Need techstream software.

 

Did you verify voltage at the PCM key on?

I haven't seen a Toyota with an electronic thermostat yet but GM has used then quite awhile on their small cars and they were really bad about leaking coolant into the connector, the connector melting, poor pin fitment, and the thermostat heaters constantly failing.


You don't have to change the VIN for it to run but the immobilizer must be reset, if you don't have the push button start it can be done with a jumper wire but if you have the push button start I believe it requires Techstream and reprogramming of the keys.

 

Testing with Key On won't work according to the description of the functionality.
The circuit is opened under a normal operation, the current flows when the coolant temperature is increasing by a large amount during high engine load driving. Likely the resistor burnt out during the short, assuming the heater circuit inside of the thermostat housing is tested and is good.
Here is SM excerpt.

 

Is the PCM different from the ECM? I so, I have not have not checked the PCM, but the engine starts, runs and shifts fine. The 4-wheel drive works normally and the antilock breaks are functioning.
I have a P0598 code, which is setting the Check Engine Light. The Check Engine light seems to be setting the Trac Contol light below 32 MPH and it also disables the cruise control. Mileage also seems to be a little worst than the normal Tacoma bad, but that could be my imagination.

I get voltage back to pin E12-22 on the ECM when the key is on.

I have a used ECM coming on Tuesday. It is supposed to be identical part number and from a vehicle with same year & engine.

I do not have push button start, so I have my fingers crossed that the jumper to the ODB2 connecter will make the antitheft happy.

 

Yes this would be the case if the PCM controlled the power side but it controls the ground side.

The thermostat heater has constant power to it with the key on therefore providing the circuit is intact and the PCM is not commanding the heater on you would see battery voltage at the PCM with the key on.

That's how the PCM is monitoring the circuit, it expects to see battery voltage there when the heater is commanded off. If it doesn't it assumes the circuit is open or shorted to ground and sets a code.

 

Toyota calls it an ECM (Engine Control Module), I always say PCM (Powertrain Control Module) except on vehicles that have a separate TCM (Transmission Control Module).

On Toyota any code that turns on the check engine light will also disable the VSC/Traction Control system.

What caused your other wiring to get fried, to big of fuse installed?

 

After you get the truck up and running you need to check if ECU calibration ID is the most recent. May need to flash ECU after. Some used ones have original ECU "tune".

 

THANKS FOR ALL THE HELP!!!!!

Got a used ECM. VIN number of the used ECM matches the year and options of my truck. I used the OBD port jumper to get the Immobilizer happy.
I rest the codes and everything seems good and the codes have not reappeared. Check Engine light stays off. The Cruise Control and Traction Control are enabled again.

Shifting is funny and it has the surge somewhere around 40 - 50 MPH. I am not sure if that will improve as it learns or if it is a sign of old firmware/calibration.

What ODB2 iphone app do I need. I have inCarDoc and it is very limited and does not seem to be able to read the Calibration ID. Once I have that info, is is there a thread somewhere about what is considered current?

Is there an iphone app capable of updating the VIN number?

 

The only phone based scan tools I know of that might do it is the ThinkDiag or the TopDon TopScan otherwise you would need a more full featured scan tool to do it.

 

Check calibration. It is probably 04b03, should be 04B04
Get obd fusion phone app. It is free. Inside the app, buy Toyota pids for your years. On Amazon, look for obd2 blue tooth adapters for your phone OS. I use veepeak for Android. Tha app will get you the visibility for all control units.
I would look for techstream app to update VIN and potentially flash a new calibration. Check with your local regional tunnig group for techstream app. Dealer will be expensive.

 

Thanks again folks!