Wiring harness (1 Viewer)

[nhall80]

How difficult is it to replace the engine wiring harness? I just pulled my fuel rail to replace injectors (one failed) and a few of the connectors are broken. I know of a few others below the intake that are also broken. Is the trouble worth it? What connections are the trickiest to get to? I know I can replace the connectors, but with several broke and the difficulty of doing that while it is still on the engine, I’d rather just replace the whole thing (if I pulled it out, I’m putting a new one in…just want to know what I’m looking at)

Thanks!

 

[ceylonfj40nut]

If I recall correctly, <1995 are no longer available. 1995-1997 are, OBD II. You can find clips from Toyota or here

Ballenger Motorsports - High Performance Electronics

www.bmotorsports.com

 

[nhall80]

If I recall correctly, <1995 are no longer available. 1995-1997 are, OBD II. You can find clips from Toyota or here

Ballenger Motorsports - High Performance Electronics

www.bmotorsports.com

I should have mentioned. My truck is a ‘95 (OBD II)

 

[Malleus]

Replacing the injector connector housings is very simple, once the upper intake is off. Replacing the engine wiring harness is simple, but not necessarily easy. You have to remove the connectors from the ECU under the glovebox, feed it though the firewall and then unplug the engine sensors as well as the two transmission harness junction connectors. IMO, these two are the hardest to get at. They sit on the frame above the starter.

You will also likely have trouble with the connectors in the head, unless you also remove the lower intake. IME, you can't unplug any of them with lower intake installed (unless they are new and clean and were lubed before they were connected) - you can't even see them. Unfortunately, this is a Hobson's choice because, unless your lower housing has been modified, the engine harness is fed through it, requiring you to unplug it before it can be removed. This is one of the reasons it's advisable to pull the engine when replacing a headgasket. There's no room to work on the driver's side of the engine (yes, it can be done, but there still isn't enough room there).

The knock sensor connector housings, as well as the sensors, are notorious for dissolving in your hands. My A/C cutoff sensor connector housing latch broke and I spent a week trying to find a solution (the housing is NLA).

There is no way I'd replace an entire harness for one, or even all of the, injector connector housing(s).

 

[nhall80]

Replacing the injector connector housings is very simple, once the upper intake is off. Replacing the engine wiring harness is simple, but not necessarily easy. You have to remove the connectors from the ECU under the glovebox, feed it though the firewall and then unplug the engine sensors as well as the two transmission harness junction connectors. IMO, these two are the hardest to get at. They sit on the frame above the starter.

You will also likely have trouble with the connectors in the head, unless you also remove the lower intake. IME, you can't unplug any of them with lower intake installed (unless they are new and clean and were lubed before they were connected) - you can't even see them. Unfortunately, this is a Hobson's choice because, unless your lower housing has been modified, the engine harness is fed through it, requiring you to unplug it before it can be removed. This is one of the reasons it's advisable to pull the engine when replacing a headgasket. There's no room to work on the driver's side of the engine (yes, it can be done, but there still isn't enough room there).

The knock sensor connector housings, as well as the sensors, are notorious for dissolving in your hands. My A/C cutoff sensor connector housing latch broke and I spent a week trying to find a solution (the housing is NLA).

There is no way I'd replace an entire harness for one, or even all of the, injector connector housing(s).

Thanks. This is exactly the info I was looking for. I was leaning toward not changing it as I’ve had the upper and lower off a few years ago and it was a beast (modified it as you mentioned so as not to mess with the harness). I didn’t necessarily want to do that again just for a few connectors.

I’ll replace the connectors I can get to and leave the harness alone.

 

[OffRoadScott]

I should have mentioned. My truck is a ‘95 (OBD II)

If it is in fact an OBD2 rig the wire harness is still available. @NLXTACY sells it on his website Absolute Wits End OBD2 Harness or you can source it from a local Toyota dealer.

I have a OBD1 rig and was able to find a known good harness and my mechanic installed it for me. It is worth it in my opinion the assurance that you have a brand new harness and likely future issues would be sensor related and the overall reliability was worth it to me.

 

[Fj80oregon]

You can buy the harness from partsouq for under $500, Witt’s end marks it up to over 650. If you get the the connectors from bellinger buy them with the pig tails and crimp the connectors then heat shrink. I replaced all mine on the last truck and soldered them and two of my connections were not solid causing me a headache. Toyota recommends crimping over soldering because of engine vibration and they can come loose.