80 Series TCM Comms issue - Won't start (1 Viewer)

[zweisman]

Hey all,

'93 FZJ80 here with ~265k miles.

Experienced an issue yesterday where I came to a stop at a red light, engine sort of just sputtered and died. I tried to restart it, and it would crank but just wouldn't turn over.

Tried again today, same result. Pulled the codes, got this: 42, 83, 84, 85.

Now, I understand the 83-85 codes strongly suggest that the ECU needs to be replaced, However, in all of the threads I've read about it, it seems as though people's cruisers still start up and run with these codes.

My question is about whether the codes could be a red herring, and if I should look for an issue somewhere else before pulling the trigger on the ECU purchase.

Thanks in advance.

 

[LandLocked93]

Look elsewhere. 83 - 85 are 'normal' for 93/94 models and not to be trusted. lol

 

[zweisman]

Look elsewhere. 83 - 85 are 'normal' for 93/94 models and not to be trusted. lol

Thanks for the advice. Any other go-tos for a truck that will crank but not start? Sputtered to death while running?

 

[LandLocked93]

Do you have a CEL (check engine light) on the dash when the key is turned to ACC or ON?

 

[zweisman]

Do you have a CEL (check engine light) on the dash when the key is turned to ACC or ON?

In the ON position the CEL is on. Which, AFAIK eliminates the possibility of an EFI relay failure.

 

[LandLocked93]

In the ON position the CEL is on. Which, AFAIK eliminates the possibility of an EFI relay failure.

Well, that and it confirms your ECU has the signals it needs to allow it to run.
You can try disconnecting the battery for a while then reconnect and see if anything changes.
After that spark would be the next easiest thing to check.
Got gas?
There are several things from there to check. A search will be far more helpful than my spitballing would provide. Thankfully haven't had to go down this road (yet ).

 

[zweisman]

I did disconnect the battery earlier for a while to see if that would help and nada. Totally full gas tank. But yea generally I'm thinking it's something with high voltage electrons.

 

[ZackR]

Start with this list (you will also find this if you search a bit):

Critical Blade Fuses
There are only three critical regular sized fuses required for the engine to start and run 15A EFI located in the underhood fuse box 7.5A Ignition located in the fuse box at the driver's knee 15A ECU-IG located in the fuse box at the driver's knee You should stock at least some 15A and 7.5 amp blade fuses if not a complete set, but those two sizes are what you need to limp home.


Critical Relays
EFI main relay, under hood fuse box & Circuit opening relay, turns fuel pump on and off, located behind the driver's left kick panel, Both of these relays are the same part number, 90987-02004, you should have one in the glove box.

Starter cut relay, for theft deterrent, usually driver's left kick panel, starter cut relay probably depends on which alarm you have, some trucks may not even have this relay.

Fuel pump relay, changes the speed of the fuel pump, bolted to the drivers side inner fender near the back on the edge of a large opening. part number 28381-16020, not as cheap but roadside repairable per Ricks instructions, so you do not have to stock this one.


Critical Fusible Links
The three Fusible Links come from Toyota as a set, all three are replaced at the same time, they are cheap, everyone should have a set in their glove box, and everyone should also carry an assortment of regular blade fuses also, "Main" Fusible link, critical as it is upstream of the 15A EFI fuse under the hood, you can test this one from the driver's seat by turning on the radio, headlights, ac/heat fan, defrost, stop light, tail lights and telephone, if any of the above work then this fusible link is good.

"AM1" Fusible link, critical as it is upstream of the ignition switch and provides the power for to the starter solenoid, you can check this one from the driver's seat by checking the horn/hazards, dome light, diff locks, rear heat, turn signals, cigarette lighter, or wipers, If you have the hazard & horn but none of the others check the big 50A AM1 fuse in the underhood fuse box (50A AM1 fuse not to be confused with the AM1 fusible link) Might not be a bad idea to stock a 50A fuse incase the big AM1 fuse blows

"AM2" is probably the most engine centric, it provides power to the ignition switch, the injectors, the igniter, the ignition coil, the distributor, and the alternator control system, if you get the yellow
light on the voltmeter with “key on engine off” this fusible link is good.

 

[zweisman]

Can you link to the instructions about the fuel pump relay?

I'm assuming that since my started is working, that it's probably not the AM1 fusable link.

Also, I get a voltmeter light with the key on so it's probably not AM2 either.

Not smelling any gas, in the engine so I do have a feeling it could be a fuel pump issue.

 

[zweisman]

Found my problem. The input wire to the distributor cap is completely sheared off at the distributor end.

 

[ZackR]

Take a photo and post it so that someone searching in the future can reference. Glad you found it!

 

[Arizona Jeff]

Here's a picture of the critical relay. I ordered new relays from Toyota (this one is not Denso/Toyota). The other two cubes are the horn relay (left) and flashers relay (right). I don't know what the other 3 ports are for but they are not critical for starting the vehicle.

Another area to check when troubleshooting is the connector for the fuel pump. It's under the vehicle. Drivers side, rear door, between the edge of the body and the frame.