Limp Mode? / Loss of power in low gears.

[humeysd40]

Hi everyone,

I'm sure this is an issue that has been covered (if so please link me to the forum).

I have an engine/drive issue with my Navara D40 07'. The vehicle starts fine without any issues/knocks or unusual sounds. Reverse actually works like normal (no reduction in power comparing to before this issue occurred). When putting into drive, the ute really struggles, then as it climbs gears it gets better, 1st-3rd has notable reduction in power (whilst blowing a load of black smoke).

Higher gears seem to drive normal. This is why i don't believe it's in limp mode?

The EGR has always been deleted, SCV is being done this week, fuel filter (engine one) been done recently, and turbo also changed in an attempt to rectify this issue (was leaking).

I also note, after some driving, it did have white smoke (one occurance) coming from the turbo area (why i replaced it) although i cant confirm where this is coming from.

Any help or other questions please let me know, need to sort this asap as i cant go offroading, camping or tow anything.

Thanks,
Humey.

 

[Old.Tony]

This is something we're only just starting to see. I'm not sure we have an answer for it yet, but let's try something: on your gearbox at the rear near the top should be TWO connectors. The uppermost should be the "PNP" (Park Neutral Position) switch and the lower is the "R" Reversing switch.

If the PNP switch is faulty it could cause issues with drive. The ECU is programmed to limit power when the ECU thinks the vehicle is in neutral (and particularly won't command large amounts of boost in the D40 when in neutral). This is done to prevent the turbocharger from overboosting which can cause other issues.

The PNP switch is supposed to have NO connectivity when in gear, and full connectivity when in neutral. This means you have a choice:

1) Unplug it and drive the car to see how it performs. If this fixes the issue, the switch needs to be cleaned or replaced. I don't know if this is a sealed (uncleanable) switch.

2) Unplug it and connect a multimeter to it. In neutral using a resistance setting, you should see zero ohms. Put the car in gear and it should go infinite (open circuit). Check all the gears.

Now if the switch is behaving ok in some gears and not in others, I'd suggest the gearbox innards aren't in good order, inhibiting the switch. This may require the gearbox to be disassembled and inspected. An oil change may suffice, but removing the switch and examining its sensor may provide some answers.

I can't think of much else that could cause this - except for the usual battery terminal corrosion (as well as fusible links etc) - these cause erratic behaviour though, not something repeatedly specific like this.

 

[humeysd40]

Hey mate thanks for the reply, is this looking from under the the vehicle or in the cabin under the middle trim?

I’ve ordered a neutral position switch. See if that changes anything.

also got an issue with the O/d off light alwaays being on, this happened when the power issues arrised, maybe corroded connections? Any help with this? (I.e the od button does nothing apart from changing the D light on the speedo gauge to gear 4).

 

[humeysd40]

Hey mate, is this the plug you’re talking about?

bear in mind its an auto? Does it make a difference

 

[Old.Tony]

The switch is on the gearbox, I'd described the manual gearbox. The auto doesn't operate the same way.

Does your instrument cluster indicate the selected gear properly?

If you're taking off from the lights in drive with 'D' indicated, you get smoke - but what if you take off with the lever set to '1' ?

The overdrive switch is supposed to send a signal to the instruments which then tells the gearbox to disable/enable overdrive. It sounds like this isn't happening properly. In my own car, I had issues with overdrive when the programming of the box (TCM) was incorrect. Nissan had to reprogram it (and didn't get it right - I had to hold the 'Overdrive' button in to make it keep overdrive off).

It's possible that your car's TCM has developed a fault. I don't think it's an issue that is easy enough for us to diagnose on a forum. Valve bodies with TCMs are not cheap (over $2K, unprogrammed) and according to Nissan, need to be reprogrammed on each new vehicle (I call BS on that). I have a valve body here that's seen a couple of hundred km (not a couple of hundred thousand, I really do mean about 300km) and it has a brand new TCM attached. I'll have to check its condition first, but if your valve body/TCM is stuffed, it's a possible option.

 

[humeysd40]

Yeah so taking off in drive or in semi manual 1st gear still produces alot of black smoke and very sluggish power. As i said it changes gears okay, and higher gears are completely fine.

Hmmm ok, can these issues happen overnight, was fjne for a massive trip i done (4,000kms) sat overnight and then it just changed into a slug. So weird.

Yeah the overdrive light is constantly on, the button doesn’t seem to turn the light off at all. The only thing the overdruve button does is change the D symbol to gear number 4. (is that normal?)

appreciate the help

 

[Old.Tony]

Yeah the overdrive light is constantly on, the button doesn’t seem to turn the light off at all. The only thing the overdruve button does is change the D symbol to gear number 4. (is that normal?)

That's not normal. When the 'D' symbol is visible, your "O/D Off" light should NOT be lit. 'D' indicates that overdrive is active (and in the older cars, it's the only gear that will allow the TC to lock up).

That's very likely a programming issue. Trouble is, when we had our TCM reflashed, they wanted over $200 for the job. Couldn't use it without though, so we had to cough up.

 

[humeysd40]

Ok so best course of action is to take it to nissan, get a tcm reflash and see what the go is?
Anything else that could cause sluggishness from the traffic lights?? (Just so i know before nissan try charge me an arm for fixing it)

 

[Old.Tony]

I don't know that I'd take it to my Nissan dealer. The problem with dealerships is they follow a very precise methodology, and that can be VERY expensive - and sometimes needlessly. An example: fuel problem? Change injectors ($4,000 + 4 hours) - no good, let's change the pump - another $4,000 + 4 hours - that fixed it, because it replaced the faulty SCV ($240 + 15 minutes).

If you trust your dealer, then by all means have at it, but this is a tough one to diagnose in text so someone with some mechanical experience is going to have to have a good look at it.

 

[humeysd40]

Alright well I've got an SCV, BCS in the post, maybe they could fix the issue. Highly doubt it, otherwise ill take it to my nissan guy who knows a little bit more.

 

[humeysd40]

Replaced my SCV and BCS, no difference. Could be a transmission issue maybe. Gonna delete my dpf maybe thats the problem, otherwise injectors

 

[Old.Tony]

Can you get the car to someone with an auto gearbox scan tool and have them run some diagnostics on it?

In particular, pay attention to the status of each gear as it's selected. Make sure that 1st gear is 1 etc.

 

[humeysd40]

Im going to replace transmission switches see if thay does anything, then off to the shop i think

 

[Liam_]

What was the problem in the end? I’m having similar troubles with mine