Thank you -- Matt.
Volvo Forums member j-dawg shows off his constructive powers by making a sweet USB charger and dash mount for iPhones and other mobile devices.
I think one of the best things about newer cars is the interior electronics. I want to be able to talk handsfree, navigate via satellite, and play music off a USB drive instead of a CD. For longer trips, I want the phone charging. But I’m a lazy child of the future, and I don’t like plugging things in, swapping things around, etc. I want to have my phone Just Work with the car, with minimal fussing about.
Modern car stereos enable most of this, and various accessories do the rest. But I am a neat freak about car interiors. I hate wires running around the cockpit, giant plasticky mounts on suction cups, things that can get lost, things that look out of place, and so on. When necessary, I’ve been charging the phone with a cigarette lighter to USB adapter and a cable. Seeing all that sticking out of my 12V port drives me into a murderous rage, and there’s nowhere in the cabin to put the phone where I can briefly and safely glance at it. So I decided to put together an in-dash USB power cable and phone mount.
MVS Forums contributor and Volvo wizard jimmy57 explains how the mass airflow sensor affects the air/fuel ratio, idle, mpg and more and various Volvo models.
On Bosch systems that is not really a MAP. It is used for boost pressure monitoring. The earlier extrapolation algorithm where MAF vs engine speed was used for boost level calculation was not as accurate. Primarily it is a feedback sensor used for turbo control valve operation.
On Denso systems where the MAP is manifold mounted it is used for lower throttle load sensing when airflow is low the MAF sensitivity error is larger. Once engine air consumption picks up then manifold pressure sensitivity diminishes and MAF is a better gauge of engine load.
MAP was the only load sensor on strict speed-density fuel systems. Volvo only used that on the Regina/Rex system on the 89-94 740/940 non turbo 230F engines.
The boost pressure sensor on the 99 and later turbo cars with Bosch system usually are noted by boost control codes. The MAF value vs boost pressure indication fall out of mapped value range. It is rarely the pressure sensor is is more likely the MAF sensor.
MVS Volvo Forums member (now Contributor) ALF1 drops the knowhow for a fix that’ll save you about $300, or much more if you’re going to purchase a new yaw sensor.
Folks – The Active Yaw Control Sensor (found under the passenger seat and carpet) is a very expensive repair whether you purchase a new unit or send yours off to be re-manufactured by Xemodex or BBA Reman or try to get a used one.
Fortunately, I found that BCM (brake control module) codes indicating a failed Yaw Sensor may not necessarily indicate a $500+ repair is on the horizon. In my case, water had not penetrated the Yaw Sensor housing. Rather, water had pooled in the cowling of the plastic electrical fitting that passed through the Yaw Sensor housing. This fitting contains the connection pins to which the harness is attached. Removal inspection showed green corrosion deposits on and in-between the pins. I assume that this somehow shorted the pins and lead to the Yaw Sensor failure codes.
I was able to carefully dry and clean the pins and female wire connector, re-install (without the water…more on this later). Clearing and rereading the codes at my Independent shop revealed DTC ABS/BCM [ABS-0012 / Active Yaw Control Sensor, sensor not calibrated] or using VIDA the code becomes [BCM-0112 AYC-Sensors not calibrated]. For under $100, you can have a shop with VIDA recalibrate the Active Yaw Control Sensor…actually its called Reprogram Anti Skid Function. That’s the short version for those who have researched the blogs as I do. More detail follows for those who do not.
MVS Forums member Jason Reed posts a fantastic write up on PTC valve electricals and function for turbo cars. PTC = Positive Temperature Coefficient.
I always wondered what was inside the PTC valve and how it worked electrically, so I decided to take apart one of the ones I harvested from the junkyard a few months ago.
I removed the rubber bushing by prying it up and off. Then I used a hacksaw to slice down one side of the main PTC tube. While I was sawing the last bit of the side, when the blade dug into the bottom piece it popped off. The bottom piece is also copper and was soldered onto the copper tube.
On the side of the main copper tube is a small 2mm diameter hole that aligns with the external small vacuum nipple. I was surprised to see how small this hole is, but when I checked the inside diameter of the vacuum nipple, it was also 2mm, so they are matched.
Next I removed the copper wall from the side of the PTC with the electrical connector. I had to pry a bit with a small flat screwdriver and I heard a cracking sound as I pried it apart to reveal the PTC heater element.
The cracking sound was from breaking the solder joints between the copper wall and the contact pin and PTC disc. I measured the resistance from the surface of the disc to the pin 2 in the connector and got ~20 Ohms, which was the resistance between the pins before I took it apart. This indicates that the resistive element in the PTC valve is the disc. The disc is soldered to the copper wall and conducts heat to the copper wall and thus to the gas passing through the PTC tube. It’s interesting that the copper wall is itself part of the electrical circuit.