UPDATE: 4/15/13
After 3 weeks of no CEL codes and the car running GREAT, I'm getting the P0128 Coolant Temp Sensor Code again. I replaced the Thermostat and Sensor already. I cleared the code and it's gone away, for now. Any thoughts? Thanks! - Geno

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First off I want to express my appreciation and gratitude to this forum for all of the GREAT posts, detective work and documentation that has been done here on behalf of Volvo owners! I have been chasing diagnostic error codes for about 3 months and have finally gotten to what seems like (knock wood!) the last of them.

I would like to contribute in some small way to the forum, so in that vein, I will post my troubleshooting journey along with some information about where I found the various parts and pieces for what seem to be to be “reasonable” prices.

Actually, Amazon.com has most of these parts in stock… and if you have a “Prime” account with them, 2 day shipping is free. I’ve shortened the Amazon URLs to make the post a little more readable.

Parts:
Beck Arnley 178-8419 Direct Ignition Coil - $40 each (2 required)
(Note: AutoZone locally carried these for $49, but matched the price for Amazon, so I got them locally and, in fact, they were VOLVO branded parts!)
Beck Arnley 178-8419 Direct Ignition Coil : Amazon.com : Automotive

EvanFischer EVA140828407 Plastic Blade-Type Male Terminal Mass Air Flow Sensor - $57 (Called MAF Sensor)
EvanFischer EVA140828407 Plastic Blade-Type Male Terminal Mass Air Flow Sensor : Amazon.com : Automotive

Standard Motor Products AC513 Idle Air Control Valve - $135 (Called IAC Valve)
(Note: NO gasket included, I made one, in case I needed it, but the existing one was in good shape, so I reused it)
Standard Motor Products AC513 Idle Air Control Valve : Amazon.com : Automotive

Beck Arnley 158-0849 MAP Sensor - $55 (Called Manifold Air Pressure Sensor)
Beck Arnley 158-0849 MAP Sensor : Amazon.com : Automotive

Beck Arnley 143-0701 Thermostat - $12
(Note: This one comes WITH the rubber gasket)
Beck Arnley 143-0701 Thermostat : Amazon.com : Automotive

URO Parts 9125463 Water Temperature Sensor - $10
(Note: My car had the 3” wire dongle connector on it, so I got this one, see picture)
URO Parts 9125463 Water Temperature Sensor : Amazon.com : Automotive

As you can see, I’ve been chasing and playing Whack-A-Mole with the codes for a while… but, as the car started running crappier (as opposed to just the CEL being on), it became an issue to deal with the root causes… My adventure detailed below.

About 3 months ago, at 132,000 miles, the CEL (Check Engine Light) came on and was showing code P0128 for Coolant Temperature Below Thermostat Regulating Temperature… But, I thought, “who cares”? Still runs well. I’ll worry about that when I need to pass emissions the next time. But then the “running” issues started.

It started to miss under hard acceleration, say up a big hill or when passing. Then it started to miss AND flash the CEL under hard acceleration. So, I thought, well, I’d better look at that… And then, after a few days of that, it lost all power completely when pressing the accelerator… Would start and idle fine, but had NO power.

And, at this point, it started showing Mass Air Flow (MAF) codes (P1101, I think). So, now it was time to do something! Had a buddy with a shop check vacuum lines, all good. Now, of course, I went to the Volvo Forums!! :-D

Based on what I had read on the Forum I disconnected the MAF sensor to check it out, and the car started running better… In fact, ran pretty well… for a couple days… Then back to the same issue. So, I decided to replace the MAF sensor. That helped a bunch… But, it still missed under hard acceleration.

So, next I replaced the spark plugs (which looked like the originals!) and wires. Ran better, but still missed a little under hard acceleration… And, the CEL would still flash when the car missed. Based on my readings on the Forum, sounded like Ignition Coils! So, I replaced those and voila, car runs better than it has for a VERY long time!

Note on the ignition coils: See picture for the replacement parts for the coils… Autozone in San Diego carries those Volvo parts. They were a little more expensive than Amazon, but I printed out the Amazon page and they were willing to match the price locally. Each coil drives 2 cylinders… The coil plugs into the top of one spark plug and then jumpers to the next. Crazy, but pretty compact!

So now the car is running GREAT! But, for the first time since we owned it, it doesn’t want to start on the first try in the mornings. (I mentioned San Diego, it’s not THAT cold in the mornings here!) It turns over fine, it just doesn’t “catch” on the first turn. I actually had to press on the accelerator pedal to get it to start. In fact, it doesn’t really want to idle very well either… unless I rev it up until it warms up a bit… Then, it runs great. This persisted for several days.

So, back to the forums… Either the Idle Air Control valve or the Fuel Pressure Regulator… I’m thinking IAC because of how the symptoms have manifested themselves. SCORE!! IAC replaced, starts like a dream again. And, is running great!

Note on IAC: This was the most expensive part I replaced at $135. You can spend WAY more in many places, but as you can see from the pictures, the Amazon unit is Volvo labeled. Several people on the Forum have mentioned cleaning theirs out as opposed to replacing it… That might also be an option if you’re on a budget. I wanted to clear up that issue permanently, so I opted for replacement.

Note on Cold Starts: The battery on this car is 5 years old and after a weekend of sitting, I can tell it’s getting a little low on battery and a little slow to start. I am planning to replace it, but haven’t yet. However, I have read on the Forums that “low / old” batteries can sometimes lead to funky codes / starting issues, etc. Perhaps that should have been where I STARTED? But, we are where we are. New battery soon! However, that said, it’s running and starting now, better than ever!

Which brings us back to the ORIGINAL Coolant Temperature Code P0128… Since I’m on a Code Dominating Mission now, I’m going after that **** too!! And, in the course of all these sensor changes / updates, I’ve picked up a P0107 Manifold Absolute Pressure OR Barometric Pressure Circuit Low Input Code… Nice, huh?

I did a lot of reading on both these codes. The temperature code seemed pretty straightforward… I opted to replace BOTH the Thermostat and the Temp Sensor, since they were cheap. Note on the picture that my car had the 3” wire dongle between the Sensor body and the actual connector. So, I got that version from Amazon. Thankfully, that was the $10 unit! Easy replacement (when the engine is COLD). A little fluid leaks out, but top off the overflow tank after you’re done and you’re good to go.

Regarding the Barometric Pressure Sensor / Manifold Absolute Pressure sensor code, apparently there are 2 identical sensors in the air intake system. One on the pre-heated intake duct coming off the radiator (Update: Apparently, this is the Inter-Cooler - Thanks GerBeGurGya!), and one directly connected to the intake manifold under one of the top manifold coverings. In reading on the Forums, some folks say try one, if that doesn’t work, try swapping out the other. I opted to replace the Barometric Sensor on the air intake duct. For me, that seems to have worked. Could have been a lucky guess!

Sorry for the LONG post, but, after 1 week all codes have cleared and stayed cleared. And the car is running GREAT!! Hopefully this information is helpful for someone else! And again, THANKS for all the help! - Geno

 

Nice,like to see people being able to find solutions for the problems taking things into their hands.If you dont mind I'd like to correct one little thing.One of the MAP sensor you say is located on the pre-heated intake duct coming off the radiator which is not correct.The sensor is on top of the inter-cooler.That plastic duct is going straight onto the throttle body.
In a way you are actually right as the inter-cooler on these cars are a bad design sandwiched between the radiator and the AC doing nothing else but pre-heat the air instead of cooling it
Again nicely done most owners would have had spend over a $1000 dollar for following the incompetent mechanic into the abyss.

 

UPDATE: 4/15/13
After 3 weeks of no CEL codes and the car running GREAT, I'm getting the P0128 Coolant Temp Sensor Code again. I had already replaced the Thermostat and Sensor, so this is a little unexpected. I cleared the code again, and it's gone away, for now. Any thoughts? Thanks! - Geno

 

Defective thermostat, pinched or exposed sensor wires, defective sensor, low coolant level. Just WAG's.

 

Could need an ECM upgrade, there's a bulletin for that.

 

Flush the coolant fill with new.The thermostat has to be a factory one.