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1995-2002 Range Rover P38A
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Discussion Starter · #1 ·
My truck is a 99 Bosch with 4.0 engine and SAI. I am running an ECU from a 2000 4.6. It runs fine, better than with the 4.0 ECU, but always throws code due to lack of additional coolant temp sensor in the bottom of the radiator. Additionally, one of the oxygen sensor connectors of the wiring harness is damaged by the previous owner. Also. my coolant temp gage works only occasionally. It seems to be a wiring issue between the sensor and the BeCM (I swapped BeCMs and measured resistance at the sensor). In my experience oxygen sensor circuits are often sensitive to resistance changes from factory values. Given all the issues above I am contemplating replacing the complete engine wiring harness instead of trying to troubleshoot and repair the old one. How big of a job is it? Can the wires be snaked through, or do I need to take things apart? I suspect that I may need to remove intake manifold. What else will need to be removed to install a new engine wiring harness?
 

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1995-2002 Range Rover P38A
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I have a little insight on this that may help.

I've replaced the engine wiring harness on my Discovery 2 with the same engine. And I purchased a P38 and parted it out, therefore removed the engine harness.

Basically you will need to remove the upper air manifold to be able to get access to the fuel injectors to unplug and plug in the new wiring. This will give you access to the knock sensor and crank sensor on the drivers side. It also allows access to the knock sensor on the passenger side and cam sensor up front. The cam sensor can be done without removing the pump but it is much easier if you remove the water pump.

Hardest part of the job is the rear O2 sensor wiring. The wiring is on top of the transmission and difficult to get access to. In my D2 I found I need to remove the center console to be able to un-secure the wiring. In the P38 I parted out I had removed the engine first then lowered the transmission so access was not as hard.
 

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1995-2002 Range Rover P38A
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188 Posts
Discussion Starter · #3 ·
I have a little insight on this that may help.

Basically you will need to remove the upper air manifold to be able to get access to the fuel injectors to unplug and plug in the new wiring. This will give you access to the knock sensor and crank sensor on the drivers side. It also allows access to the knock sensor on the passenger side and cam sensor up front. The cam sensor can be done without removing the pump but it is much easier if you remove the water pump.
Thanks for your insight and detailed info, I really appreciate it. I took the upper intake off once before, when I replaced the coils. I figured the upper intake had to come off. Just wasn't sure what else needed to come off.

Hardest part of the job is the rear O2 sensor wiring. The wiring is on top of the transmission and difficult to get access to. In my D2 I found I need to remove the center console to be able to un-secure the wiring. In the P38 I parted out I had removed the engine first then lowered the transmission so access was not as hard.
I suspected that rear oxygen sensor wiring was going to be a pain. The rear oxygen sensor wiring is a PITA on Disco II, so no surprises there. I'll snake my endoscope (best $35 I ever spent on an inspection tool) between the transmission and the transmission tunnel and try to see how the wires are run and whether they are attached to the body of the car or the transmission. If they are not, I'll figure something out, may be make a tool for the job (I have a number of machine tools at my disposal).

Push comes to shove, I can remove the driveshafts and the transmission mount and see if I can move things around a bit to make some space. Worst case I'll remove the radiator and move the engine with trans, but I'd rather not.
 
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