Trans ECU Help? (1 Viewer)

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May 22, 2016
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Houston
Hi guys!

Does anyone know where the wiring harness for the A442F ECU is grounded?
Does anyone know the correct way to measure inspect the voltages of the trans ECU?

So I have what seems like solenoid trouble. I am following the troubleshooting guide in the tech manual (this seemed like a good idea). And I get stuck on STEP 1: Read diagnostic code.

I jumped the OBD port as shown in the tech manual - nothing. The OD OFF light is supposed to blink steady if everything is ok and blink a code it has one. Nothing. The ECU must not have power, I think.

So I find the section on the ECU and start checking the terminals as shown below.
94-land-cruiser-tcu-connections-page-1-jpeg.581758
94-land-cruiser-tcu-connections-page-1-jpeg.581758


With the ignition switch in the ON position:
  • I get nothing anywhere, so I measure across PWR to GND on the plugs - nothing.
  • I got a weak response from the brake pedal pin (approximately 0.5V off and 0.8V on).
  • I got no continuity between the ground pin on the plug and the body so I'm not sure if it is related.
  • I observed no change with the engine running or not.
There is also a check engine light, but I am still waiting for my OBD-to-OBDII adapter to arrive.

This leads me to believe there is a problem with the ground of the harness - or I just have completely no idea how to measure this stuff correctly (which is also true).

So this leads to my questions:
Does anyone know where the wiring harness for the A442F ECU is grounded?
Does anyone know the correct way to measure inspect the voltages of the trans ECU?

Thanks in advance!
 
Have I gone where no Mud'r has gone before?? But it's only my second post! Anyone? :crybaby:
 
As we say in the emergency medical field " Can you describe what the main problem is?"

When someone says they have no voltage anywhere, the first thing I think of is the fusable links. But that is nothing more than a wild guess without knowing what your main problem actually is.
 
Yes the main problem is the 80 takes off from a stop in 3rd gear (or maybe even OD) when placed in D. If the shift lever is moved manually from L to 2 to D, it seems to shift normally (although abruptly). All accounts suggest a solenoid is bad (or a couple).

I thought it was wise to follow to the troubleshooting advice in the tech manual. Doing that, it seems i have no signal from the transmission computer at all. Further inspection seems I have no power to the computer at all. No computer = no solenoid action.

I did find the ground (it's behind the driver's side kick plate) and I got continuity between that ground and the ground in the plug.

I'm going to go back over all of the terminals again.
 
sorry, I forgot to say -- Thanks elhombre! Yes I forgot to mention all of the fuses are good. Unfortunately.
 
Well, I can tell you that the TCM is the same unit as the Engine ECM. I can also tell you that the 93 models like mine had a problem with them that causes the TCM to stop communicating with the ECM and the transmission stops shifting properly as far as shift points go. If you're not starting in 1st you should ensure your shift linkage is properly adjusted as well as the transmission throttle cable is properly adjusted and then ensure you have adequate fluid flow through your cooler and adequate fluid level in the transmission. After all of that has been confirmed the EWD can help you establish wire color code and the transmission section of the FSM will walk you through the trouble shooting of solenoids and where to find the specific points in the wiring to inspect.
 
Well, I can tell you that the TCM is the same unit as the Engine ECM. I can also tell you that the 93 models like mine had a problem with them that causes the TCM to stop communicating with the ECM and the transmission stops shifting properly as far as shift points go. If you're not starting in 1st you should ensure your shift linkage is properly adjusted as well as the transmission throttle cable is properly adjusted and then ensure you have adequate fluid flow through your cooler and adequate fluid level in the transmission. After all of that has been confirmed the EWD can help you establish wire color code and the transmission section of the FSM will walk you through the trouble shooting of solenoids and where to find the specific points in the wiring to inspect.

Thanks LandCruisin. I also have a '93. Do you know more about the problem that causes the TCM to stop communicating with the ECM?
 
Thanks LandCruisin. I also have a '93. Do you know more about the problem that causes the TCM to stop communicating with the ECM?
It's a common internal issue, only cure is to find a 94 ECM
 
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