Mechanics

TPS PROBLEM OR CPU PROBLEM

2008 Dodge Caravan • 88 miles

Ok, some info first. 2008 dodge grand caravan. Two weeks ago I change the plugs and used sea foam to clean the intake. Later that day, it started running extremely bad and had warning lights on dash. I was getting code for mass air flow sensor. Changed mass air flow sensor. Then the o2 sensors would stop working after about 10 min of idle. Changed both o2 sensors. Restart and everything was fine for about 10 min, then rough idle and warning lights. Changed plug wires. Same thing. Got code p0113 and p0123. Throttle position sensor reads at 100%(5 volts) even without car running. Car has been running fine for 2 weeks, but still have warning lights and tps stays at 100%. Used multi meter and checked tps wire harness without it plugged to tps. 2 wires read 5 volts. Checked wire connections on gas peddle, is fine. Running out of ideas.
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Mstamrs
October 12, 2012.




What engine and trans? How was SeaFoam introduced? What terminals on TPS have 5volt refference?


Docfixit
Oct 12, 2012.
3.8 ltr auto trans, sxt trim( I think). Sea foam was sprayed into throttle body, thats why I changed air flow sensor thinking I could have damaged it by getting some on it. I dont know how to explain which terminals had 5 volt reading. Its a 6 terminal plug and the 5v readings are on opposite corners if I remember correctly.


Tiny
Mstamrs
Oct 12, 2012.
5 volts only on terminal 2 middle top row


Docfixit
Oct 12, 2012.
5v on middle and 5v on bottom opposite side of plug. See photos.


Tiny
Mstamrs
Oct 12, 2012.
Allow me to interject a couple of notes. Chrysler has never used a mass air flow sensor. What you might have is a throttle-by-wire system and you're disconnecting the throttle body.

Second, the voltage readings are irrelevant when you measure them with the plug disconnected. That creates an open circuit. The position sensing part of the circuit has mechanical stops that prevent the signal voltage from going beyond, (approximately), 0.5 to 4.5 volts. This type of circuit will always have a "pull-up" resistor or a "pull-down" resistor in the computer to force the voltage to go to an unacceptable level when there's an open circuit. That's one of the ways it knows to set a diagnostic fault code. Without those resistors, when you unplug a sensor it is possible for that signal voltage to "float" to some random value from being connected to all the other circuitry, and if that random value is between 0.5 and 4.5 volts, the computer will accept it and try to run on it. You need to carefully back-probe the terminals through the rubber seal and take the voltage readings with that plug connected.

When you unplug the throttle position sensor, the signal voltage is going to go to 5.0 volts. That's where you're getting the fault code from. Most scanners read voltage, not percent, but that's irrelevant. Code 113 is related to the intake air temperature sensor unless they have changed with the new "CAN Buss" system.

P0113 Intake Air Temperature Circuit High Input

High voltage again means that sensor was disconnected.

P0123 Throttle/Pedal Position Sensor/Switch A Circuit High Input

That is also caused by unplugging the connector while the ignition switch is on.

How are you determining the oxygen sensors are quitting? Two of them yet. In the absence of fault codes, you would need a scanner to view live data to see what they are reporting. Which warning lights were turning on? If you have multiple lights, that suggests low system voltage from a charging system problem. Of course it could be from disconnecting things too while the ignition switch is on.

Based on your observations that the problem started shortly after replacing the spark plugs, I'd start there by double-checking the gap, heat range, and proper seating of the plug wires. Some people say certain brands of spark plugs don't hold up in certain engines. I've read a lot of solutions that involved fancy plugs like split-fire types and things like that. If the engine didn't come with them, they seem to cause some problems. I've had plug wires on my cars in the past that I didn't seat properly and they arced and burned away until a misfire resulted.


Caradiodoc
Oct 12, 2012.
Ok, I think I am following you. I will have to test the wires while plugged into the throttle body. I do have an obdII program on my laptop that gives me real time readings. That was how I knew that the o2 sensors seemed like they were shutting off. However, I have cleared these codes numerous times. They come right back on. The warning lights are the check engine light and the Ignition light(lightning bolt in parentheses). The van is not drive by wire, It has a sending unit on the gas pedal and no cable wire to the throttle body. If I start by taking a reading on the wires to the throttle position sensor( throttle body and tps are all one unit on this model.)And move the butterfly open, it should give me a better understanding whether or not the tps is bad or not. Correct? And by the way, I really appreciate your time and knowledge on this problem. You have been the only one that has pointed me in a direction.


Tiny
Mstamrs
Oct 12, 2012.
Oh, and the sensor that I have been calling the mass air flow is the sensor that is in the intake tube between the air filter and the throttle body. I am not sure of the exact term for it.


Tiny
Mstamrs
Oct 12, 2012.
"The van is not drive by wire, It has a sending unit on the gas pedal and no cable wire to the throttle body."

That's a contradiction. If there's no cable, then you do have throttle-by-wire. That is the only system that uses a position sensor on the gas pedal.

I've never worked on one of those but I have read a lot of horror stories on them, particularly Volkswagen problems. I know enough about them that I don't want to get involved due to the high potential for lawsuits. I suspect the lightning bolt warning light is related to this system, and because of the seriousness of its reliability, you might not be able to erase codes related to it. That might require a regular scanner or the dealer's equipment, but based on how the events transpired according to your original post, I suspect there is a defect and that's why the fault codes keep coming back.

Logic dictates those codes are not related to rough running because throttle problems affect engine speed, not single cylinder misfires. The biggest clue you have, if you're seeing on your laptop what the Engine Computer is seeing is that 100 percent throttle position. Try watching that value while wiggling on the connector. If you see it change, the most common cause would be a stretched terminal in the connector. You can usually remove a plastic locking wedge, then lift a retaining finger to pull a terminal out to squeeze it tighter. Next, if you know from a wiring diagram which terminal is the signal wire, you can back-probe the connector to measure the voltage right there. If it agrees with the value shown on your laptop, either the sensor is defective or its ground wire or terminal is open. If you find a different voltage than shown on the laptop, there is either a break in that wire or a glitch with your software. There could also be a stretched terminal in the computer's connector but that would be very uncommon.

As for that sensor in the intake tube, that is where they used to put the intake air temperature sensor. (It had two wires). Unplugging that would have set that 113 code. Some manufacturers put that sensor right inside the throttle body, and I was wondering if that's why you have six wires there. For the tiny bit I know about the throttle-by-wire throttle bodies, those motors that run the throttle blade are real strong and use really large gauge wires to handle the high current, so I'm guessing you have a second connector to it with bigger wires. That's what left me wondering why there were six wires in the connector in your photos.


Caradiodoc
Oct 12, 2012.
The dodge and the vw vans are the same. Just different emblems. The pic I sent is the whole throttle body. Tps and throttle body are all one piece. No other wires except the 6 in the pics I sent. No cables, no other wires. I guess "by wire" means electrical wire, not cable( like an older carbureted motor ) which is what I was thinking. Anyway, do you think I should change the plugs to another brand? Like I said, all I did was change the plugs and clean the intake. Then everything went bad. I guess what has puzzled me the most is that the codes keep changing. First was the sensor on the intake, and the dodge garage told me that was most likely what was wrong. Then the o2 sensors. Now its the TPS. Im looking for direction from someone who has more knowledge about this type of thing. No chance of any legal repercussions from my end. Let my know if I am on the right track. First, check wires and connections to the throttle body. Second, change spark plugs to something different. Third and hopefully final, change to a new throttle body. What do you think?
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Tiny
Mstamrs
Oct 12, 2012.
Boy, if that's true about VW and Chrysler being the same I'm going to be very depressed. VW is one of the top three manufacturers in the world for being customer-unfriendly as far as the tricks they design into their products to cost owners money after the sale. Chrysler is in the top three of customer-friendly manufacturers.

Volkswagens are well-known for computers locking up from doing the things you're doing on your van. Simply moving the throttle blade by hand under the hood causes a mismatch between the throttle position sensors on the pedal and on the throttle body, and that will do it. On some models the engine will not start. If it does, it won't increase speed above idle no matter what you do with the gas pedal, and it will not come out of park. I've heard a lot of stories about people having to drag those cars skidding off the hoist, onto a flatbed truck for a REAL expensive trip to the dealer to have multiple computers unlocked and to have "minimum throttle" relearned. Simply disconnecting the battery to replace it can result in the same disaster. A lot of do-it-yourselfers are getting caught with the "got'chas" they have designed in.

I have a friend who buys and rebuilds smashed Chrysler products and haven't heard any of these stories from him yet. To us, "German engineering" is nothing to be proud of. It's just different, and sometimes bizarre.

That's not to say you can't have German parts on your van. In particular, Chrysler buys their fuel injectors from Bosch in flow-matched sets and they have WAY fewer problems than almost any other manufacturer. One of my Grand Caravans has a Bosch starter and alternator too, but that's as close as they come to German engineering.

Seems to me I did hear something once about another manufacturer buying Caravans and putting their name on them but I didn't pay much attention. Maybe that's what VW is doing.


Caradiodoc
Oct 13, 2012.

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