I have a 2000 S40 with about 75,000 miles. In the last few weeks it has been hesitating while starting. When I first turn the key, it doesn't crank at all. Usually, it takes two or three tries before it cranks and starts. Then the other morning, I went to start it and it made a pretty bad grinding sound. Almost like gears slipping. I thought that the starter was going out.

So, I brought it to Auto Zone and had the codes pulled. Here's what I got:

P0128 -Coolant Temperature
-Below Thermostat
-Regulating Temperature

The quick reference guide said to check the Coolant Level, then the Thermostat and then the Coolant Temperature Sensor.

The coolant is low, but would that or the other items cause it to start like that?

Your help would be appreciated.

 

Replace the coolant temp sensor and thermostat.

 

The Volvo dealer referred to it as an IAT Sensor. Auto Zone called it a Water Temp Sensor. Are these all the same?

Thanks

 

Sounds about right.

Volvo has about 3 different names for one sensor.

 

gota love the swedes makin up three different names for one thing

 

Yep thats what I say.

 

I replaced the thermostat and the water temp sensor. It seems to start a little better, but still hesitates sometimes. The check engine light is still on because I haven't had the codes re-set. Will re-setting the codes help at all? Or is there something else that I should do?

FYI: I also pulled the neg battery terminal and cleaned off some corrosion. Someone told me that disconnecting the battery would re-set the codes. They were wrong.

Thanks for all the good information. You saved me about $300.

 

Clearing the codes might help.

If it doesn't let me know Then I will tell you something else to look for.

 

I had Auto Zone clear the codes and the check engine light came right back on. It's still hesitating on the start. Any ideas would be appreciated.

 

The code came back for the coolant temp sensor?

Also check the Fuel pressure regulator.

Pull the vaccum hose off the regulator and see if there is gas in it. If so the regulator is bad.

 

He didn't re-pull the codes. I'm not sure why. Maybe he just assumed it was the same issue.

Just to make sure I'm looking at the right thing. The Fuel Pressure Reg is on the right side of the fuel rail (when looking at the engine) and it's a plastic assemblywith an aluminum canister looking thing (which I'm assuming is the regulator) coming out the bottom and the whole assembly attaches to the fuel rail?

If that's correct, is the vacuum hose coming into the top or the bottom? There is ahose with a fittingthat plugs into the top of the plastic housing and there is a rubber tube that connects to the canister.

First I removed the hose (which seems to be metal with rubber over it) on the top of the assembly. That had some gas in it that drained out. I removed the entire plastic assembly from the fuel rail and removed the canister (regulator?). The canister had some gas in it as well.The rubber tube attached to the canister didn't want to come free and I didn't want to force it.

Hopefully this all makes sense. Thanks for your feedback.

 

One more thing. I noticed in an earlier post that your referred to the schrader valve. Is that the tube that connects to the top of the assembly?

 

Check the hose on the bottom.
Yes that is the regulator.
The schrader valve looks like a Valve stem for a tire.