Transmission not functioning unless glow lamp is on

[FJhammer]

Posted this over in the 70 series forum but thought I'd post here as well in case someone here has any idea.

Recently purchased a '99 HZJ74 with an A442F transmission. Upon delivery, I went to drive it and it initially wouldn't shift out of 1st gear. If activating the 2nd gear start, it would shift into 2nd no problem. Turn 2nd gear start off and I'm back to 1st only. Then the glow plug indicator lamp lit up and suddenly the transmission has full function. Shifts are smooth and timely, everything functions as it should. I took it out on the highway and after about 20 minutes the glow plug indicator goes out briefly (2 min) and it automatically kicks me out of OD. Lamp comes back on and OD activates again. Also power feels reduced compared to the 1HZ in my HZJ73.

I've searched and can't come up with anything that matches what's going on. I've seen some posts on how the glow lamp on the 1HDT-FE is actually a CE light as it doesn't have glow plugs at all but rather a heated screen on the intake side. I'm not sure if that carries over to the 1HZ or what year that began if it did. If it is solely a glow lamp indicator, I can't imagine why the glow plugs would be coming on and staying on for extended periods of time or why it would effect the function of the transmission. I've also read that there may be issues with the EGR vacuum lines, as that might be reducing power but I fail to understated the correlation to the glow plug indicator and the simultaneous reaction from the transmission. I've gone over the vacuum lines and they're all pliable, no splitting or cracking, and look it great condition.

Is the glow plug indicator on the HZJ74 actually a CE light?
Why am I limited to first gear when the GP indicator is out?
Why do I have full function when the GP is lit?

Any help would be greatly appreciated.

 

[Squash]

Not a clue, but will follow this conundrum while you wrack your brain.
Most likely some dodgey wiring and/or a bad ground.

 

[FJhammer]

Not a clue, but will follow this conundrum while you wrack your brain.
Most likely some dodgey wiring and/or a bad ground.

Yeah, I don't think anyone does. I've posted here and the 70 forum and gotten lots of looks, only one response from you. Lol

 

[ikarus]

Posted this over in the 70 series forum but thought I'd post here as well in case someone here has any idea.

Recently purchased a '99 HZJ74 with an A442F transmission. Upon delivery, I went to drive it and it initially wouldn't shift out of 1st gear. If activating the 2nd gear start, it would shift into 2nd no problem. Turn 2nd gear start off and I'm back to 1st only. Then the glow plug indicator lamp lit up and suddenly the transmission has full function. Shifts are smooth and timely, everything functions as it should. I took it out on the highway and after about 20 minutes the glow plug indicator goes out briefly (2 min) and it automatically kicks me out of OD. Lamp comes back on and OD activates again. Also power feels reduced compared to the 1HZ in my HZJ73.

I've searched and can't come up with anything that matches what's going on. I've seen some posts on how the glow lamp on the 1HDT-FE is actually a CE light as it doesn't have glow plugs at all but rather a heated screen on the intake side. I'm not sure if that carries over to the 1HZ or what year that began if it did. If it is solely a glow lamp indicator, I can't imagine why the glow plugs would be coming on and staying on for extended periods of time or why it would effect the function of the transmission. I've also read that there may be issues with the EGR vacuum lines, as that might be reducing power but I fail to understated the correlation to the glow plug indicator and the simultaneous reaction from the transmission. I've gone over the vacuum lines and they're all pliable, no splitting or cracking, and look it great condition.

Is the glow plug indicator on the HZJ74 actually a CE light?
Why am I limited to first gear when the GP indicator is out?
Why do I have full function when the GP is lit?

Any help would be greatly appreciated.

Do you have EGR? Does that EGR use an ECU?

Don't know if this helps but maybe can give you a couple more things to look into. In later model diesel 80s w/ 1HD-FT/A442F and EGR, the EGR, transmission and glow systems are connected. For example, I believe the transmission, glow, diagnostic and EGR wiring harnesses are in the same wiring loom. Also if your EGR is removed or not working, you'll get a permanent glow light on the dash. According to the ERM111E FSM for the EGR system, the glow plug light is part of the diagnostic setup, AKA a CEL light. Codes and diagnostic methods start on page 2-13

https://forum.ih8mud.com/resources/repair-manual-for-emission-control-1hd-ft.147/

When you manual swap it I've heard that the tach won't work unless you leave your EGR ECU connected.. sounds like the signal goes from trans or IP -> EGR ECU -> cluster. I haven't confirmed that since I'm in the middle of the swap right now but that's what I've read.

Also in digging through my HDJ81 I found that some shop in the past had put a scotch lock in a really inconvenient place in the wiring going into my EGR ECU - I assume it was for an alarm or remote start or something - you know how crazy the wiring and accessories can get in Japan. Could be worth looking into the state of the wiring and if it's been messed with?

 

[FJhammer]

That’s definitely helpful. It has an EGR system and I pulled the dash and went through all the wiring and found the ECU. I also pulled the cluster and went through all the lights and confirmed there is no CEL, So I think you’re right that the glow lamp also doubles as the CEL. I tried hooking up both readers I have and neither one will communicate with the truck. I went through all the fuses and interestingly there’s a spot for a glow plug fuse however, it’s empty and there’s no wiring to it on the back of the block. I do have glow plugs and not the heated screen so I’m not sure why there’s a spot in there that’s not utilized or where the power for the plugs is getting routed through.

I was originally thinking it was an electrical issue but now I’m wondering if this is an EGR fault. Would that affect the system in such a way that it limits the function of the transmission?

I’ll start going through the emission control manual you linked and see if that gives any insight.