2000 Non-Turbo S70 Idle dipping when coming to a stop

[00VolvoS70NonTurbo]

Hey guys/gals,

First post here but I love the forum so far. Just bought a 2000 Volvo Non-Turbo S70 2 months ago with some minor problems. So far I've very much enjoyed the ride and love the car overall. The couple issues I am dealing with are as follows:

1) The idle will dip down after I've been driving when I come to a stop. Once I have fully stopped it dips to about 400 rpms and then about 1 or 2 seconds later it goes back up to 900 rpms and idles just fine. I'm guessing this is some kind of ETM issue from what I've been reading but I have a few questions. The car only has 87,xxx miles which seems appropriate for an ETM issue. The check engine light pulled these codes - P0225 - Throttle/Pedal Position Sensor/Switch "C" Circuit... Does this require a brand new ETM? Could a cleaning possibly fix the issue for another 10,000 miles or so? Could I buy one of those $140 eBay ETM things that fixes the rubbing sensor issue? Or is my only option a $600 ETM replacement? Maybe it's not ETM related and that code means something else?

2) It's also pulling codes P0135 - o2 Sensor Heater Circuit (Bank 1 Sensor 1) & P0130 - o2 Sensor Circuit (Bank 1 Sensor 1) I believe that means its for the upstream o2 sensor correct? The Volvo replacement is about $300 which also seems insane. What is the difference between that Volvo one and a $40 generic o2 sensor that just needs to have the wires spliced?

3) A/C does not work and when I went to recharge it, it wouldn't accept any refrigerant and was showing really high pressure like 110 or so I believe. Also pulling code P0532 - A/C Refrigerant Pressure Sensor Circuit Low Input... Does this mean the pressure sensor to release the pressure just isn't working? If the sensor is replaced the rest of the A/C system should be fine? A/C would be nice but isn't necessary. If it's a $100 fix then I might do it, if it needs a new compressor and is going to be $500 then forget about it.


Sorry for the long first post. Any and all help is greatly appreciated. Thanks!

[jblackburn]

Welcome to MVS.

Yes, those codes are for the front sensor. Replace the O2 sensor, clear the codes, and go from there. This idle dip symptom is indicative of a vacuum leak or mass airflow/O2 sensor discrepancy on the non-ETM cars.

The low pressure AC sensor is on the passenger side near the base of the windshield. Unplug the sensor and briefly jumper the connector with a paperclip and see if the compressor kicks on. If that works, that's probably all that needs to be replaced.

[00VolvoS70NonTurbo]

Welcome to MVS.

Yes, those codes are for the front sensor. Replace the O2 sensor, clear the codes, and go from there. This idle dip symptom is indicative of a vacuum leak or mass airflow/O2 sensor discrepancy on the non-ETM cars.

The low pressure AC sensor is on the passenger side near the base of the windshield. Unplug the sensor and briefly jumper the connector with a paperclip and see if the compressor kicks on. If that works, that's probably all that needs to be replaced.

Thanks for the response! Regarding the O2 Sensor, does it have to be the $300 Volvo one? I'm located in California, what is the most affordable O2 Sensor I can purchase? I see some for $30 and some for $300.

The vacuum leak or mass airflow sensor problem: Would the first step be for me to clean the mass air flow sensor and throttle body area and see if that helps? I'm not sure I understand the non-ETM cars thing you mentioned, I was under the impression my 2000 S70 has an ETM.

And thanks again for the AC sensor advice, I'll try that this weekend.

[jblackburn]

The non-turbos use a Denso O2 sensor (Volvo rebrands it and marks it up); part number 9202309. I would stick to Denso; these cars tend to not like cheap aftermarket sensors. There are several Volvo parts vendors (see some of the banners at the top of the site) that sell this - I would take a look around for the best price.

I would start with the O2 sensor - you have obvious codes there that indicate the sensor itself has gone out rather than the typical O2 sensor codes that are set for a vacuum or air leak. If you replace the sensor and the idle dip continues after a day or two of driving, then set out to clean the MAF sensor/throttle body and check for vacuum leaks. The car may take some time to adjust fuel trims and idle behavior back to normal once replacing the sensor.

My 98 is a non-ETM car and exhibited that idle dip as a direct result of what was usually a vacuum leak; I cannot speak for sure about the later ETM models like yours. However, that happened because the MAF and O2 sensor values weren't agreeing, which is exactly what's happening with your bad O2 sensor.

[mikealder]

My 2000 V70 with the Denso engine management system used to rev dip when pulling up in a similar way to what you describe, after about two years it threw the P0135 code so I changed the pre cat Lambda sensor and it hasn't rev dipped since. After spending hours checking part numbers of lambda sensors I decided the Denso DOX-1419 sensor was the correct unit for the car, purchased a new one for £106 (about $160) fitted it and haven't had a problem ever since, no rev dipping and no issues.

The P0255 code is for the accelerator pedal position transmitter, you can remove this take the cover off and clean the wipers/ resistance tracks with an electronic cleaner. Removing the upper outboard bolt that secures this unit in to the car is a challenge as you can't see it so work only by feel - Once the unit is out of the car it is obvious how the cover comes off - Mike

[mikealder]

The above picture shows you what the resistive tracks look like in the accelerator position transmitter - Mike

[00VolvoS70NonTurbo]

Wow... Thank you all so much! Step 1 will be to order that Denso part and get it installed. I will let you all know the results.