Recently my 2001 Volvo S40 T1.90 has been throwing codes PO171 and PO236. Today I cleaned the MAF with CRC MAF cleaner. When I first took the car out for a test drive it was running like I have never seen it run before (great). Then I tried WOT at 50mph to test a passing situation. The car kept hesitating and then accelerating the whole time(hesitate, accelerate, hesitate, accelerate, etc.). I tried this about a six times and it did the same thing every time. Twice I could hear a clicking sound... don't know what that was. Then when I came to a stop light it idled fine but when the light turned green is hesitated a lot. I thought it was going to stall but it didn't. It ran fine while I was driving normal but would hesitate when I started from a stop. Then it started running fine again while I was driving normally. Anyone got any suggestions on what to do next or what this might be?

 

Are you still getting any codes?

P0236 is for the boost pressure sensor aka map sensor.

There's a very good discussion about those codes here:

http://www.justanswer.com/volvo/37wp...ago-asked.html

 

Thanks for the link bw77... that sounds exactly like my problem.. I'm going to check out the map sensors. My wife also got the codes right after filling up her gas tank.

 

Replaced the MAP on the intake and still having hesitation on hard acceleration. I bought an Innova 3100 scanner and cleared the codes but they haven't come back yet even though the car is driving the same. I can't figure out how to get to the MAP sensor on the Fuel rail ( I believe it is). My scanner gave me this Freeze Frame info... does it mean anything helpful?

=== Stored Error Code(s) ===
Error Code: P0171
Possible Causes:


=== Pending Error Code(s) ===
Error Code: P0171
Possible Causes:

Error Code: P0237
Possible Causes:

Error Code: P0237
Possible Causes:

Freeze Frame Information:
1. DTC for which Freeze Frame was Stored - P0171.
2. Fuel System 1 Status - Closed Loop.
3. Fuel System 2 Status - Not Supported.
4. Calculated LOAD Value - 25.10 %.
5. Engine Coolant Temp - 188.60 °F.
6. Short Term Fuel Trim - Bank 1 - 14.06 %.
7. Long Term Fuel Trim - Bank 1 - 8.59 %.
8. Intake Manifold Absolute Pressure - 17.47 Inhg.
9. Engine RPM - 1,770.00 Rpm.
10. Vehicle Speed Sensor - 50.33 Mph.

 

I think you need to figure out how to replace the other map sensor.

This guy had a similar problem.

https://volvoforums.com/forum/volvo-...n-p0107-35376/

 

Looks like the same problem bw77.. thanks. Anybody know how to get to that 2nd on on the fuel rail? I can take off the black cover and unbolt the aluminium shield but it is attached to some wires from the left and fuel line from the right.

 

I've been chasing the same problem. I just replaced the MAP under the fuel rail this weekend. Mine is running great now, no problems! Cleared codes. Life is good again.

It's very easy to change. Takes about 5 minutes. Remove the plastic cover above the fuel rail (2 hex bolts). Then, reach in from the upper side of the fuel rail and unplug connector to the MAP. Then use an end wrench to reach in from the under side of the fuel rail and remove the small bolt holding the MAP down. I used a screw driver to carefully "pop" the MAP out of the hole. I did remove the two bolts that are circled in the picture on this thread but I'm pretty sure you can remove the MAP without pulling those bolts.

 

Thanks for the response. I am assuming that if you removed the two bolts I circled then you didn't removed that metal shield too much as it is attached pretty tightly to hoses. I am going to give this a try.

 

Yes, that's correct. By removing those two bolts it did give me a little extra room. It still "flexed" a little even though it was still connected to all of the hoses.

Funny thing, the dealer quoted me over $100 just to diagnose the problem plus another $117 for the MAP sensor + 1/2hr labor to replace. Almost $300! I bought one online for $82 and replaced it in 10 minutes.

 

I got it thanks to the help here at volvoforums.com. I wish I would have just gone for it last week but I had trouble pulling that connector off the MAP sensor. Ended up getting a pair of pliers and using it to squeeze the release and pull off at the same time. It was easy to remove the bolt actually with a ratchet after I took the two bolts off the shield. Put the new one on and it is driving normally now. Going to drive it to work tomorrow for the real test. Have a 25 mile drive all highway to work. Can't believe and $80 dollar part was causing all that trouble. Even worse that that little plastic doohickey cost $80 but glad to do it myself and save money. Got the Innova 3100 scanner to help diagnose and clear the codes. I am going to take it back to Costco and get a better one. The free scan at Autozone doesn't cost as much and does everything the 3100 does except clear the codes. IPD has a couple for less money that do much more. Still trying to figure out which is the best and am going to start trying to do all the maintenance myself on the S40. Thanks again for everyone's help.

 

Glad to hear you got it swapped out.

If you have a portable pc, check out autoenginuity. I don't have it, but have
heard good things about it. Not cheap, but it has add on software for gm, etc.

 

I spoke to soon. Got in the car this morning to go to work and it started to idle rough as I was backing out of the driveway and threw another code. I won't be able to check the code until I get home. The car is driving better in that I can drive normally and there is no noticeable problem but if I try to give it a lot of throttle it starts hesitating. If I give 1/4 throttle it drives perfectly and the turbo kicks in but more than that and it hesitates bad. I'll check the codes when I get home and follow up here.

 

Checked the codes when I got home:

P0107 Boost Pressure Sensor Signal Too Low
P0302 Misfire Detected in Cylinder 2
P0237 Turbo boost sensor A circuit low Volvo S80

I cleared the codes and swapped the replaced MAP sensor for the old one still in the car that wasn't replaced and left the new one in. It is still hesitating just like before but no codes now. I am stumped

I think I am going to have to check out the autoenginuity scanner. I need something that will give me real time data to study and figure this out. I guess it could still be the MAF
Conditions For Setting This Code: Possible Causes: Monitor Information:

Conditions For Setting This Code: Possible Causes: Monitor Information:

 

I think I have finally resolved this problem and wanted to post what I found in case someone finds this with the same or similar problem in the future. I want to thank everyone for their help. When it came down to it it was this post that was identical to my problem and sent me on my way to a resolution:

http://www.matthewsvolvosite.com/forums/...lit=fuel+filter

I think the cause of most of the confusion is that I seemed to have two different issue arise at once. The only one that coded was the MAP issues. I replaced the MAP sensor and my codes went away but the symptoms the car had did not. Incidentally there was a poster who had a similar issue and the exact same codes and he replaced the MAP sensor on the air intake by the intercooler (which Haynes actually calls the Intake Air Temperature Sensor but it is identical to the MAP sensor) however it was the MAP sensor on my intake manifold where the fuel rail is located that I had to replace.

The car ran and started perfectly with an occasional hesitation at idle but didn't happen much and was gone as soon as it started. I could not accelerate hard past 1/4 throttle or the car would start hesitating like crazy and if I keep my foot in it the check engine light would start to flash for a few seconds and then go away.

Once I read the post from the link above I decided to start concentrating on the spark plugs. I replaced them and it ran much better but still had a slight hesitation at WOT. Then I replaced the coils and spark plug wires and the problem is gone. Those codes had my attention focused on the boost and it's related sensors but when I was not getting anywhere I started thinking it was the fuel filter. I did a search on that and came to the post above which was identical and there I found my solution.

 

There seems to be some confusion still.There is two identical part doing the same thing basically.Both measuring pressure.Then there is a sensor for the Air Intake Temperature.The IAT also located at just after the IC right next to one of the pressure sensor.The other pressure sensor is on the manifold.
Now whats happening is that the sensor measuring seemingly the pressure in the manifold it has nothing to do with it.It measures atmospheric pressure and nothing else.It has no access to the pressurized air in the manifold.
The sensor after the IC is the one measuring the boost but the ECU uses both the boost and the atmospheric sensor to calculate the actual pressure.

 

Hi Guys.

Atfer replacing the TCV due to codes P0236 & P0237; now still showing the same codes as pending simply by turning the key to the ON position.
ECM will not clear them.
My question is: Does anyone know what the proper return voltage, of the MAP sensor, to the ECM should be.
I only get 0.3V seems too low.

Thanks