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Discussion Starter #1
Hi,

I would like to get input from those who are good with electronics to help come up with a way to make a PCM think it has an engine attached. I know it should be possible. Our local emissions testing requires that all OBD-II vehicles be plugged into a computer, then started and idled for a few seconds to check for emissions issues.

For the sensors that only send a constant voltage signal back (such as a TPS), resistors could be wired in. But there will be issues with items like a CPS, cam sensor, etc. There will also need to be substitutes for injectors, ignition system, etc. so it thinks its running an engine.

Anyone have any ideas on how to go about wiring up something like this?

Jim
 

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I put a thread about this a while back. I am looking at swapping into a 96 explorer which is obdII. If MA says it's illegal I'm going to try to build a circuit that will replicate all the needed signals. Some have said it won't be easy but I guess we'll see.
 

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You need to research the megastim project. It is part of the megasquirt offering and is used to test the megasquirt ECU. I know it can provide the needed inputs for all your basic sensors. For the ones it may not have you need to measure what the sensor is at a given condition and you can likely use the resistors to duplicate it if you need. Injector and ignition firing could be a bit more tricky. It depends on how "smart" the system is. If it just sends out an open loop signal to fire and is not closed(requiring feedback), then you should be fine with a constant load like a resistor. However some ECU's measure the feedback from the injectors and coils firing. If that is the case, you will be hard pressed to duplicate the feedback from them without using the actual parts.
 

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It may be easier to fool the scan tool than it is to fool the computer..

Possibly build a box that will make the scan tool think it's attached to an OBD-II computer?

Or maybe do a custom program on the ECU to have it act stupid? Might be possible to pass through your actual sensor readings (or at least what few you want - RPM, engine temp, B/MAP, whatever) to make things look "legit" to the scan tool? (No idea if that is feasible, just throwing stuff out there..)

It's all going to depend on just *what* they look at when they attach. I can think of a few simple and quick things that you're capable of doing with a scan tool that would completely blow the lid off this, and I'd not put it past them to have some of it part of the test.
 

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Hi,

Our local emissions testing requires that all OBD-II vehicles be plugged into a computer, then started and idled for a few seconds to check for emissions issues.

Jim
I plan to install a 4BT with a ZF 5-42/BW1356 into a 1998 Durango. We have similar requirements in Louisiana. We are also required to have all original emissions equipment installed. I have given this some thought and have some ideas. I HAVE NOT TRIED THESE AND I DO NOT KNOW IF THEY WILL WORK! Here are my thoughts:

Coolant Temperature Sensor (CTS) - Install in the 4BT in place of the original.

Air Charge Temperature Sensor (ACTS) - Install upstream of turbo charger air inlet

Throttle Position Sensor (TPS) - Attach to injection pump linkage. Search the site - it's been done.

Manifold Absolute Pressure Sensor (MAP) - Try to wire in a resistor. If this doesn't work, wire it to the TPS. Use diodes in both the TPS & MAP to "electrically isolate" them. Wiring to the TPS should simulate engine load as the MAP does in the 4.7.

Crankshaft Position Sensor - Use a 6BT balancer; make a bracket to align the sensor to the balancer. You may have to machine additional "marks" on the 6BT balancer to match the Durango. This should also feed your factory tachometer. I believe Diesel Durango has this in the works.

Camshaft Position Sensor - Mount it facing the front of the 6BT balancer. Count the "firing marks" that the Durango sensor uses and divide by two. (Crankshaft makes two revolutions per one camshaft revolution). Machine the marks on to the 6BT balancer. It may be necessary to properly "time" the camshaft position sensor marks with the crankshaft position sensor marks to satisfy the computer.

Oxygen Sensors - Wire in resistors. If needed for visual inspection, Install sensors into exhaust piping, cut/ splice resistor(s) into wiring near computer.

Battery Temperature Sensor - Leave it in its present location.

Ambient Air Temperature Sensor - Leave it in its present location.

Oil Pressure Sensor - Install in the 4BT in place of the original.

Transmission Oil Pressure Sensor - Try wiring in a resistor. If this doesn't work, try installing into 4BT oil system. It will see varying pressure with engine RPM.

Exhaust Gas Recirculation (EGR) - I don't think the 2000 4.7 has an EGR. The 1998 5.9 does have an EGR. I plan to install it downstream of the turbine exhaust and plumb it upstream of the turbo compressor inlet. IT WILL BE BLANKED OFF AND WILL NOT RECIRCULATE EXHAUST TO THE INTAKE!

Fuel Injectors - Try leaving the wires disconnected. If this doesn't work, try wiring in resistors. The injectors are probably high impedance (12 - 16 ohms).

Catalytic Converter - Gut the converter, remove the inlet and outlet pipes by cutting the pipes on the converter side of the welds, slide a piece of exhaust tubing through the gutted converter and weld to the converter body. This should satisfy the "visual" inspection. Check the link for a better description.

http://www.lunghd.com/Tech_Articles/Exhaust/Copy_Cat.htm



If anyone has any ideas on this, I'd like to hear them.

Mike
 

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You guys really need to do some reading on how engine management systems run thier onboard diagnostics so you can understand just how impossible what your trying to do is going to be.

The megastim will work to fake the megasquirt that has zero onboard diagnostics or emissions components. It's not going to work for an obdII computer.

You could get a good education on the list at diyefi.org. The guys that designed your durango engine management system are probably there and can tell you what your up against.
 

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F250 is really right. As I think about this more, the oems have alot more going on than the diy units. They are alot "smarter" and will most likely code out.
 

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Discussion Starter #13
Our system is very simple. It doesn't adjust the RPMs or control the engine in any way- it just reads it to check 2 things- 1. That the engine is running, and 2. That the MIL is not on (no current codes stored). It reads everything in about 5 seconds or less. It doesn't care which manufacturer's computer its reading- we have fooled it by using a GM car for a Toyota inspection, etc. Its a pretty "dumb" system. There are simpler systems than the Dodge that could be used as a substitute...although the 5.9 uses the older, more primitive system than the 4.7.

Here are some of the thoughts I have come up with- Use a computer from a manual trans vehicle...that will eliminate any auto trans sensors. For many of the items, such as injectors, they could be wired up to the computer without being in an engine. Just wire up the parts and mount them inside a box. As 95Z28A4 mentioned, most of the sensors can be installed in the Cummins to get actual readings.

Jim
 

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NHdiesel - if you fooled the emissions computer by plugging in another car, why don't you just do that at inspection time?

Has anyone thought about a stand alone fuel management system like the impy guys use? One of these might be easier to fool than an oem computer.
 

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Our system is very simple. It doesn't adjust the RPMs or control the engine in any way- it just reads it to check 2 things- 1. That the engine is running, and 2. That the MIL is not on (no current codes stored). It reads everything in about 5 seconds or less. It doesn't care which manufacturer's computer its reading- we have fooled it by using a GM car for a Toyota inspection, etc. Its a pretty "dumb" system. There are simpler systems than the Dodge that could be used as a substitute...although the 5.9 uses the older, more primitive system than the 4.7.

Here are some of the thoughts I have come up with- Use a computer from a manual trans vehicle...that will eliminate any auto trans sensors. For many of the items, such as injectors, they could be wired up to the computer without being in an engine. Just wire up the parts and mount them inside a box. As 95Z28A4 mentioned, most of the sensors can be installed in the Cummins to get actual readings.

Jim
The computers nowadays are NOT as stupid as the ones in the early, pre-OBD days. Unless the computer can confirm that it's in command of the engine and that the sensor data it's getting is accurate, it's going to throw codes. So, even if the inspection station doesn't do any exercising of the vehicle computer, the built-in test protocols of the computer are gonna throw codes if it doesn't get the expected reaction to the commands it sends.

In your case, with the simple testing done by the inspection stations, a computer re-programmed so that it's pretty much brain-dead (which could be quite a challenge unto itself) would probably work.. Until the state wises up and starts making the tests a bit more sophisticated. The simpler solution is the one you've already given: the old switcheroo.

There is another solution: Use an actual OBD-II engine / computer / all in your swap. The question there is when did OBD-II hit the Cummins. I don't think CI (Compression Ignition) engined vehicles were required to have OBD-II until 2004. And I don't know if the equivalents to the 4B in those years are OBD-II compliant..
 

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You know, you could just let me register you in Arkansas as a diesel, there's no inspection here, and very very relaxed to vehicle changes/swaps/engines/etc., then transfer the title to your homestate with the correct stuff - wouldn't that work? :)
 

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Discussion Starter #17
I'm not worried about my inspections at all- I do just use a substitute vehicle if needed. This is more of a "Gee, I wonder..." kind of thing. I am mostly just putting the challenge out there to see what you all come up with.

Jim
 

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Use a computer from a manual trans vehicle...that will eliminate any auto trans sensors. For many of the items, such as injectors, they could be wired up to the computer without being in an engine. Just wire up the parts and mount them inside a box. As 95Z28A4 mentioned, most of the sensors can be installed in the Cummins to get actual readings.

Jim
The computer from a manual trans vehicle sounds like a good idea. In the case of the Durango, are you referring to a same year Dakota with a manual trans?

As a last resort, stuffing the injectors into a sealed box may work. Radio Shack has different sized boxes.

http://www.radioshack.com/product/i...&cp=&sr=1&origkw=box&kw=box&parentPage=search

Mike
 

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My 98 Jetta diesel has the OBD II plug in the dash.
Through it you can receive codes (like the bad glow plug wiring harness it has now).
It can also be used to adjust how it runs and performs to a certain extent.

I had a computer chip put in it by Jeff at http://rocketchip.com/ his website is quite old, but he is still working in cars, and very very knowledgeable (he wrote the codes for the performance chips).
I went to his shop to have the chip swap done, once the computer was removed, taken apart, the new chips installed, he had a dummy "car" set up on the bench complete with dashboard n which he checked the computer to see if it was functioning before it was put back in the car.

So, he essentially had a "car in a box" something like that may work, and I am sure Jeff would understand how to go about it, although he seems to be extremely busy.

Grigg
 

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Onboard diagnostics know the engine's running and sensors are operating correctly by continuously throwing off A/F ratio and watching how the sensors react at operating temperature. The computer has to have a sufficient log of these events taking place and succesfully passing many times in order to NOT have stored trouble codes. If that wasn't the case anyone with an OBDII scanner could clear thier cars codes in the DEQ testing parking lot and pass.

Not only is the computer linked to the engine, but it's linked to atleast the vehicles speed, transmission and throttle position- All inputs very hard to duplicate.
 
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