[gkmotorsport]

Hi all, first post from a long-time lurker!

A disclaimer: my car is actually a Kia Cee'd, but I've basically exhausted every Kia specific source I can find and I get the impression a few people here really know the engines well so...

My Cee'd has suffered from the dreaded 'limp mode' problem for just over a year now. At times it has improved, at times it has been worse, at times it has lunched the turbo, and right now it's being held back by the ECU. The following list is the shortest possible version of what I have tried, in order(!):

- Replaced diesel filter
- Replaced air filter
- Replaced MAF sensor and BPS/MAP sensor
- Replaced a worn out ring clip on the turbo's inlet
- 2 cans of Wynn's turbo cleaner and a can of DPF cleaner
- Jiggled the actuator on the turbo countless times
- Had the turbo replaced (the shaft snapped while accelerating but incredibly did not then eat the oil or take anything else with it!)
- Replaced oil and filter (the previous filter was literally the wrong size even though a Kia dealer fitted it!)
- Sprayed numerous sensors and contacts with switch cleaner
- Read the entire Limp Home Mode thread here. End to end!

The most consistent fault codes displayed via OBD are p0098 and p0238, both of which point firmly at the BPS. According to Autohex, persistent p0238 causes the ECU to switch off the EGR, limit fuel intake, and fix boost pressure to 900 hpa. My car 'suffers' from slightly better fuel economy when playing up, and I can hear the turbo spinning when over 2000 rpm, so I'm sure this all matches up.

I found a *very* detailed inspection guide on another website, which explains how to verify the proper functioning of the electrical bits. However, I seem to find every time I check that the power and signal voltages on the BPS harness are 5-6 V when they should be between 4.8 and 5.1 V. I'm not an electrical expert, but this sounds to me like a bad wire somewhere in the harness.

Has anybody else looked into this bit of the wiring, or had problems with this sensor? I saw that some people had a good outcome after replacing the entire loom, but this is quite expensive to pick up in Germany and I want to rule out any stupid mistakes I might have made!

Very grateful for any advice, of course.

[gkmotorsport]

Oops, I received the message that this thread has been moved, and realised I hadn't been too specific about why I posted in the i30 forum.

The Cee'd is essentially identical to the i30 under the skin - the engine and electronic systems are 100% interchangeable, so I was hoping that someone with the same problem on the i30 might be able to share some wisdom

[Bogdan1986]

Sounds like a nightmare, gk. I did a google search for your error codes and among the possible causes are faulty wiring and/or faulty PCM. Especially the BPS, if the reference voltage shows over 5V, it points to either bad wiring or faulty PCM.
Did you check the reference voltage for the IAT sensor in the MAF?

@adrek , can you give some insight?

[tw2005]

The most concise list would be this:

Tried everything, please help. Get it all the time , sometimes even shorter. Drives us nuts  @nzenigma

I'm trusting since it says 1.6 in your profile it's still the original motor D4FB  not the  1.7L D4FD in the i40. Also if you've snapped a turbo shaft, what distance has this done? I've got one of those too at 377 000 K

I'm just going to list what the i30 has for tose codes trusting it'll be similar to Kia. I've had no issues with any of mine in the motor department and only had diesel since 2016 so very much a novice but we have had some reports here on on the motors being powered back .


This is from MD Elantra 2007

p0098

[tw2005]

Just about to list P0238, first thing I notice is P0098 has no failsafe so it's not cutting power, P0238 does

[tw2005]

[tw2005]

[Paolo39]

You have problem with IAT sensor P0098:

Internally failed #2 IAT sensor (new can be still faulty, especially aftermarket one)
Faulty connection at #2 IAT sensor
Open in IAT ground circuit or signal circuit
Short to voltage in IAT signal circuit or reference circuit IAT
harness and/or wiring routed too close to high-voltage wiring (e.g. alternator, spark plug cables, etc.)
Faulty PCM (less likely but not impossible)

Read more at: P0098 Intake Air Temperature Sensor 2 Circuit High
Copyright OBD-Codes.com

I hate those flow chart, because they do not teach logical thinking. You need good auto electrician/diagnostician with preferably osciloscope to look at IAT.
You will have to check 5V reference (preferably on few sensors, not only IAT), power, grounds, harness to ECM, at last the ECM could be at fault (good ODB scanner with live data needed).

Code P0238 is more likely the result of problems with IAT. This DTC could be related to intake air temperature sensor (IAT), engine coolant temperature sensor (ECT), or 5 volt reference.

Read more at: P0238 Turbocharger/Supercharger Boost Sensor A Circuit High Input
Copyright OBD-Codes.com

[tw2005]

[tw2005]

Keep in mind the pin outs at the ECU connectors may not match

[Dazzler]

Wow! some great responses there already. Keep up the good work. 

[tw2005]

Here's CUD-A  shown for 2009 i30 with DPF

[nzenigma]

You have problem with IAT sensor P0098:


  logical thinking.
 You need good auto electrician/diagnostician with preferably osciloscope to look at IAT.
You will have to check 5V reference (preferably on few sensors, not only IAT), power, grounds, harness to ECM, at last the ECM could be at fault (good ODB scanner with live data needed).

Tw2005 has provided far more info, than I can. 
As a technician, the above advice is sound. Get the right equipment.
This common theory that a new loom will fix the problem is flawed. Rarely does wiring fail , but a leak or short in a single wire is easily traceable and reparable.
Like tw Im surprised at the turbo failure as described.

[mickd]

Glad you guys are on the case.
I'm so totally lost,  may never get home.   

[tw2005]

Glad you guys are on the case.
I'm so totally lost,  may never get home.   

same, I just copy and paste It's tragic I now have to rely on grey imports to the forum for techo stimulation

[nzenigma]

techo stimulation

  

[tw2005]

techo stimulation

  

Wa wa Nee

I see your imagery skills are improving

[gkmotorsport]

Hi all,

Wow, that's a flood of useful responses! Sorry for the late reply, my body decided that the best thing to do with all of this information was to deploy a nasty cold...

In answer to individual posts:

@tw2005 - It is indeed the D4FB; I'm at 224,000 km and going strong apart from this. The turbo died about 6k ago.

@Paolo39  - The sensor itself was replaced. I did find early on that a lot of the guides are quite vague when it comes to OBD codes. This car doesn't have a single IAT sensor; the job is shared between the MAF and the BPS.

@nzenigma  - Thank you! It's all so clear now

Based on the advice - particularly that the problem is rarely the loom itself - I traced some of the other connectors from the same branch of the loom and spotted that the wires to the 'VGT Control Solenoid Valve' connector look a bit old; one is actually missing a tiny spot of insulation entirely.



I remembered that I had to unplug this when I replaced the oil filter, and that it ran perfectly for a few days after that, and gave it a good wiggle before reseating it. That was on Tuesday, and it has been boosting *almost* normally since then.

There are still a couple of jerky moments occasionally, so I think something is still loose or making poor contact. I will deploy my multimeter and contact spray tonight or tomorrow and let you know if anything interesting is seen.

[Dazzler]

Thanks for the update.  That is sounding promising.   

[nzenigma]

@gkmotorsport

Thanks for the update. It is possible that you are in the right area. In the past, I have had issues with  that Solenoid Valve because it is quite vulnerable to impact in that position.
While checking the connector etc, also have a good look at the rubber hoses and the plastic outlets. There may be a crack in one of them.

[gkmotorsport]

@gkmotorsport

Thanks for the update. It is possible that you are in the right area. In the past, I have had issues with  that Solenoid Valve because it is quite vulnerable to impact in that position.
While checking the connector etc, also have a good look at the rubber hoses and the plastic outlets. There may be a crack in one of them.

Really sorry to gravedig my own topic, but I've not had too much time to properly look at this over the past few weeks and have resorted to reseating/wiggling/shouting at the cable every few days. I just saw your reply and wondered if it might be more of a problem with the valve or vacuum lines rather than the power supply. When I did manage to check the connector with a multimeter, there didn't seem to be any drop in voltage as I moved it around.

Have you (or anyone else reading) removed the solenoid before? Is it simpler than it looks? My source for nice detailed pictures no longer works, and it does seem to be mounted on some kind of clip rather than bolted to anything. I can't quite get my head around it though.

[nzenigma]

Yes just pulls away from the clip. Easy job.