Hi everyone



I’d love your advice. My 2003 Discovery II has already been a labor of love.

I got a P38 engine installed 1.5 years ago when my previous engine blew up.

Since then it has been working great. Never had any problems with it. Just did a 3k road trip, no issues at all. I took it in for a DEQ test and they couldn’t proceed due to various codes popping up. Took it into a garage and they told me it’s gonna need a big overhaul. Transmission specialist alone said I need to change the transmission for $3k. I’ve just had a newborn so money isn’t flowing, so any advice on which of these codes are a priority or not. As a reminder, it runs and works great. No slippage is obvious.

What am I looking at here?! Any advice on a Pacific North West (I’m in Portland, OR) expert for any of these (transmission and beyond). And advice on any of these I can fix myself (I’m an amateur but eager to learn)?



Transmission codes:

P0734 Gear 4 Incorrect ratio

(I’ve been driving this around town in manual to take the pressure off 4th gear). (Picture attached of the trans fluid color).





Engine codes:

P0154 O2 Sensor Upstream catalyst bank 2

(This has been a consistent problem. Engine light on constantly but was told it wasn’t a big problem)



P1000 (75) Catalyst Damaging misfire multiple cylinders

P1000 (70) Misfire Cylinder 8 With Cylinder Cutoff

P1000 Catalyst damaging misfire cylinder 8

P1000 (35) O2 Adaptive mixture correction TRA bank 2

P1000 (27) O2 Adaptive mixture correction TRA bank 1



P0172 Mixture Adaptation FRA bank 1

P1000 (249) Leakage Detection Module - leak detected



P0175 Mixture Adaptation Factor FRA bank 2

P0155 O2 Sensor Heater Upstream Cat Bank 2



Would love your advice. I love this vehicle so much. I expect to pay to keep it running. I know it’s worth the time and attention. Thanks

Sam

 

Change the MAF, spark plugs, wires, coil packs and O2 sensors. Trans is fine, that code get's thrown when the MAF is starting to go out.

All of these things are easily done with a little patience and the whole lot of parts is not a large sum of money either. Coil packs are the only part that is a little tricky but it's still a simple job overall.

 

My advice: Do not go back to that shop. Run from that shop. Listen to whowa004.

In Portland, what garage did you take it to?

I've always been treated fairly at Green Oval... Especially when other shops told me I needed to spend $10k. Their shop rate is not cheap but they have never tried to upsell me or do any service that was not needed.

Nice looking truck! Welcome!!

Learn and do as much as you can yourself... All the info you will need for the basic stuff is on this forum or a youtube video.

 

@whowa004 and @Dave03S are right while you are at you may as well service the transmission. Fluid, filter and gasket it is not a big deal or cost.

 

This.

I've killed a couple MAF sensors and the codes that pop up stay off once the sensor is replaced.

 

Thank you so much. All three of you.

i’m going to buy a MAF (MHK100800LR or Bosch 0 280 218 010) and start there. I’m guessing changing a MAF should be pretty easy starting point.

And then attempt the rest, as you mention I might get someone else to do the coil pack but I’ll go for the rest. Are there any specific wires, spark plugs, O2 sensors you’d recommend?

and thanks for the heads up on the tutorials here. It really is an amazing collection of people, these forums.

Thanks for the love on the vehicle.
I feel lucky to own one.

I did use Green Oval and they can be good. But I’m hoping this’ll be cheaper than the usual visit to them!

I’ll have a crack at this and I might reply back if I have big problems.

 

MAF is super simple just be gentle with the clips that hold it to the airbox lid as they are notorious for breaking. I'd go with the Bosch unit for the MAF. That may solve all your issues tbh, fingers crossed. Plugs I use some E3 I think they are from O'reilly's on both my discos with no issues, wires I believe I have some Kingsborne (can't think right now but pretty sure that's it and 8mm). If doing wires you. might as well do the coil packs. If you don't have SAI it can be done without pulling the intake manifold off but it's a huge pain so I'd recommend just pulling the intake and saving some pain and anger lol.

 

STI wires and NGK plugs have been working fine here...

 

thanks so much for this. Super super helpful. 🤞🏼 the MAF fixes it all. I’m hopeful.

 

thanks Dave