Limp mode problem once hot - 06 C30 T5

Post by **scot850** » 06 May 2025, 14:17

A new Volvo owning friend of mine has bought this car knowing it had some kinks sorted. They ended up having to have the head replaced as they discovered a crack in the head (never heard of that on a 5 cylinder head). So after about $5000 CDN of work the car was fixed but now when it gets hot is suddenly goes into limp mode until it is cold again.

He suspects it may be a wiring issue but a busy life means he has not enough time to work on the car. He says he suspects the issue might be a wiring harness issue, but looking into that, he says that that wiring harness for the turbo engine and the lighting the car has is no longer available from Volvo. Has any of you out there with a P1 had anything similar to this?

I know one code he had was for a throttle body issue (replaced) and the 2nd one I think was a air leak issue but it was also taken care of.

I am in the process of getting the car dropped off with me so I can spend some time with Vida to see what if anything shows up.

Any of you come across a similar issue?

Thanks,

Neil.

Post by **scot850** » 06 May 2025, 15:51

Some additional issue. Error codes (the ones he can remember) were:

1) P2108 - Throttle body error
2) P2281- Air leak between the MAF and TB.

There have been other errors. I am trying to arrange for the car to be dropped off on the weekend and I'm gathering together a plan of action to look into the issue. I have Vida to use as well to hopefully get more detailed info.

Thanks,

Neil.

Post by **volvolugnut** » 06 May 2025, 17:35

I had a similar issue with 2001 T5. It would occasionally not start or stall when hot. It turned out to be the ETM. XeMODex replaced 1 or 2 year old ETM at no cost to me.
I have details somewhere in a thread.
volvolugnut

Post by **scot850** » 06 May 2025, 23:16

This car does not have an ETM like the cars up to 2002. It uses the later style (late 2002-) throttle body which does not need programming. The car owner says he had this swapped out when he got the code as it is for his daughter so not cutting corners. I don't really like working on P1 engines, particularly the turbos as they have a weird layout with little room to work with.

I intend smoking the intake system to see if there are any leaks there, also clean the MAF. I might even remove the TB to check it has been seated correctly and tightened up.

Naturally I will get Vida on it as well. I have just got my newer version from David at Boot & Go so hope to try to get that running as well to see if it running faster than my old 2014A version.

Appreciate the help!

Neil.

Post by **scot850** » 27 May 2025, 21:21

Well back to updating on the limited progress so far. Currently stuck waiting for a TCV from Volvo. Can't understand why it now takes so long to get parts at the local dealers. 10 years ago when I worked in parts for a short time, if we ordered parts that were in one of the West Coast US warehouses we would have the parts the next day. Now it takes 3-7 days to get any non-stocked parts. So much for progress.

The more I have worked on this car, the more bodgery/sloppy work I find. I hate having to clean up after 'professionals'!

Having cleaned and tested all the relays in the CEM and Main fuse boxes, as well as fiber glass brushed the fuses and coating the contact areas with No-Ox-ID (see the link below):

viewtopic.php?p=663695#p663695

I have swapped the badly corroded +ve battery terminal clamp (see above thread) with a used one.

I have confirmed the wiring harness for this car is unique to the 2007 C30 (it changed when the engine went from a T3 to T7 designation in 2008), the engine harness (NLA from Volvo) is different but no one knows why. Several other parts are different too, including:

1) The alternator (not sure why)
2) Starter motor (different exciter wire. Old - female spade terminal, New - eyelet and 10mm nut).

The harness have some differences. Still trying to figure those out. Problem is that I pulled the whole 2011 S40 T5 engine harness, but the car had a fairly heavy front end shunt which has damaged some of the harness. I wasted time today trying to figure stuff out only to find varying results. Eventually found some damaged harness sections.

The harness took close to 6 hours to pull. I could have done it a bit quicker, but there were so many broken plastic parts and bent connectors it took much longer accessing stuff. Basically had to remove many ancillaries just to get to connectors.

I plan to cut a couple of parts out of the harness to repair some issues with the harness in the C30. I found the exhaust CVVT solenoid wiring harness had both wires damaged (not broken), and also the TCV harness (they had covered it with tape).

One error the car gave me was the TCV signal low. Could the damaged wires caused this? Possibly. I will repair those sections and then plan to run the car to see if the issues return. So far other than these damaged wires there is no smoking guns I can see. Currently I am seeing the potential issues are:

1) A bad overheated battery with possibly a bad +ve post which is leaning following overheating from overcharging caused by the engine ground from the cylinder head to the RHF strut tower not being re-attached after the 2nd head repair/replacement. Battery voltage is also lower than I like so suggested to the owner we change it to eliminate it.
2) The ECU may have been damaged when overcharging. Might explain multiple error codes and then a Limp Mode message. Issues are random and have no direct connection other than the ECU/ECM.
3) The TCV may be bad. I have tried cycling the one in the car (a swine to get to) and testing the resistance. These do go bad and the error code is a multi-offender. I will repair the wiring and drive the car while waiting for the new one. I will then replace the TCV harness up to the cylinder head from the S40 harness to ensure it has not been pulled internally when it was damaged. TCV may not be bad but to do the wiring, and for $90 CDN considering how hard it is to access it and the connector, I'll change while in there.

From my PnP junkyard run I got relative bargains as they had a 40% off everything you pull that weekend! Yay!!

I pulled as part of the harness removal:

1) The ECM/ECU. - Undamaged. Although from a later engine, and not a direct swap, it can be cloned and has the same Bosch part number. Xemodex do a cloning service if you supply a unit. Still it is $400 + Tax + shipping both ways. So not cheap. A lot cheaper than a new one (approx. $1600-2000) + tax/shipping + programming!

2) Intake and Exhaust cam sensors - Same part number for T3 and T7 variants

3) Alternator - Not the same. Not clear why yet. Both 150Amp units and I think the connectors are the same but need to confirm

4) Starter - Again not the same. Definitely the exciter wire is different.

5) MAF - This is the same.

6) Throttle Body - Again the same and no programming needed.

7) Engine wiring harness - Again different. Slightly different connectors but more research needed. It may be swappable with some connector changes

Ignition Coils - Older but not cracked at all under the boots like used ones usually are. Look like new - These do not fit P2 which I thought they did

9) TCV - These are the same for both engines. The resistance I tested for the one on the car and the used one were close to each other, so I am having doubts, but they can fail when hot. So not off the table yet.

Neil.

Post by **scot850** » 29 May 2025, 00:14

Well, I am not sure where to go now. I repaired 4 damaged wires but honestly don't think they were a real issue (yet).

I still cannot access the car with Vida. Tomorrow I will try my newer version now that has been set up and see if there is any better luck. I don't know where to go with this now.

If the new version does not work (my Autel can read the Vin# and other data), how do you diagnose the CEM or ECM if you can't access them? I am reluctant to send the ECM to say Xemodex for testing unless I can be confident on the part being the issue.

For Xemodex to fix the ECM (Assuming they find and issue and can repair it) is around $800 CDN with shipping. They can clone the ECM for around $500 with a supplied ECM (which I believe I have). The unknown with that is is came from a front end crashed S40 T5. There is no physical damage to the casing, but it is possible it could have been damaged internally with the accident.

Any suggestions out there?

Thanks,

Neil.

Post by **scot850** » 29 May 2025, 17:29

Great news. After all the cleaning of the Main fuse box and the CEM, as well as the wiring repairs, today I tried my new laptop and Vida 2014D and it worked!! I was able to connect to the car and read it ok. As the battery has been disconnected a few times, the only issue that came up is a fault with the radio/CD player (the CD player chunters away for a while when the key is turned to Pos-II or the car started). The owner is aware of this issue.

However, when doing the testing, I had my 2A trickle charger attached as I always do. After about 5 minutes the low battery warning came on. No wonder this car needs such a big battery. What the heck is it running? The radio and fan are off, the DRL's are on. I can't think what is doing such a draw on the battery. The battery was only at 12.0V!

With 970CA/790CCA it should not have discharged that fast, which I believe is tending towards the battery possibly has a bad cell. Anyway a new battery is coming tomorrow so I can fit that and re-check the current drain. If all is good, it is time to start testing the car.

I have had great support from the dealer service manager I know at one of or local dealers. They have been very helpful indeed.

Neil.

Post by **scot850** » 09 Jun 2025, 10:51

Still no further forward. The problem is that new issues come up each time the car is driven! I have no idea what I am trying to fix on this possessed car!

Last drive, car ran great (I added 3 gallons of gas as it was low, just incase!). However, once back in the garage, and trans in park, the idle went up to 1300rpm? Blipped the throttle and it dropped to 800-850 rpm then started 'hunting' and went up to 1000 rpm?

Add to that, the turn signals went crazy! They work ok for actual turns (like 90 degree) and cancel, but if you change lanes and turn the signal on, it will not cancel. It turns the signals for the other direction on?? It never did that in the previous 2 test runs?

Final straw was switched the engine off, removed the ignition key and the dash and headlights stayed on?? Put the key back in and turned to PosII and off again and heard a positive click and all was ok? Ignition switch issue as well? What the heck???

How can one car keep generating all these random issues? I'm thinking it is either an CEM or ECU or both may have damage from the engine ground not having been refitted. Now the ignition switch and the turn signal issues are both well documented P1 issues. The turn signal switch looks like it was made with high precision chinesium plastic and parts that vaguely are designed to fit together. Sort of thing you expect out of a Christmas cracker from the Dollar Store.

I will add that although I can now get Vida to access the car, it will not let me access the live date section. The button for that stays greyed out.

Was 'forced' into another junkyard run. Found 2 samples of the missing vacuum clip for the end of the turbo car intake plenum that were missing causing a vacuum leak. I will add a thread on that for others for a future reference on a work around as Volvo do not sell the 30c clip, you have to buy the whole intake plenum for that at around $400 CDN!

Neil.

Post by **scot850** » 13 Jun 2025, 19:57

Well, threw in the towel and called in reinforcements! I arrange with one of the local dealers to drop the car off yesterday morning for 1 hour of diagnostics.

Naturally the car ran perfectly all the way there and they could not find any issues as like me they found no codes. By the end of the day even the service manager had rolled up his sleeves and had taken the car for a long run and nothing. They asked if they could keep it overnight as he planned to take it for anther run this morning.

Well, I got a message at lunch time it had thrown a code for the MAF going AWOL. So they planned to throw another MAF in. Naturally I could not authorize that on behalf of the owner as the part is well over $600 CDN and more from the local dealers plus taxes and fitting. (Labour rate is $200 + Tax/hr CDN). They laughed when half an hour later, while on the way to a friends I dropped by and left a good used MAF. The question was how could I have one available...........?

So that is now the MAF, ETM, TCV, battery and I'm sure there was something else all gone bad in 2000km? Can't believe that is possible for a car with just over 100k miles.

Anyway, I did not expect to hear from them again as the manager was in a meeting for the afternoon. Well at about 4pm another message. Thanks for the MAF, but now the car has thrown another code for the BCM (Brake control module). They are like me finally getting towards the idea the issue is possibly wiring or in one of the modules. So they asked to hang o to the car over the weekend so they could take another look on Monday!

So, while I can't truly expect them to do all this work for nothing, technically I have still not been asked for more! I did make the point that although the mechanics are experienced, they are all relatively new to Volvo's so it was an ideal learning challenge for diagnostics!

I guess we will see where this goes. I have a used ECM and CEM if needed for cloning purposes. The dealer does not do this but Xemodex do. Price is about $500 each for cloning assuming the donor parts are good. If not they can get over $700 for repairing the originals or for the CEM if they supply a donor it is nearer $900 CDN. Yikes!

In cases like this you can easily understand how a car can be mechanically totaled.

Neil.

Vova585 · Post by **Vova585** » 13 Jun 2025, 20:22

What a nightmare. I hope that shop will just want to use this car as a lerning opportunity, but doubt they will play with it for long. Maybe they can look on wiring diagram if MAF and BCM are sharing any common wire?(5v reference, ground?) It is possible that both items are possessed with electronic gremlins, but i doubt.
All this makes me miss mono injector days and hand crank windows.