2002 V6 ECU question

lostintexas · Aug 20, 2010

Like the title says, I have a 2002 V6 which is my "workhorse". It's my commute car and I've had it since 2002.

I've been having problems with it and have had it in the shop twice to get it resolved and 2500$ later it's still at the same point.

Last time I went it they said they thought it might be the ECU and said they would change it for 800$, well I'm leary because I've spent 2500$ and still nothing resolved and they "think".

OK so I've gotten 2 ECUs from ebay and I've tried both of them on my car and what I'm getting is the engine turning but not starting.

Do I need to get the ECUs reprogrammed or something? Any guidance would be welcomed, I really would like to keep my mustang.

For more information on what's going on with the car, piston No6 is not firing.

Thanks

wmburns · Aug 20, 2010

What have you done regarding the anti-theft system (PATS)? What is the theft light doing?

FWIIW, if only a single piston weren't firing, the motor would still "hit".

How are you trouble shooting the spark?

Where did you get the PCM? Is the PCM from the same model year and transmission type (manual/auto)?

lostintexas · Aug 23, 2010

wmburns said:
What have you done regarding the anti-theft system (PATS)? What is the theft light doing?

FWIIW, if only a single piston weren't firing, the motor would still "hit".

How are you trouble shooting the spark?

Where did you get the PCM? Is the PCM from the same model year and transmission type (manual/auto)?

The theft light flashes, should I be looking for something specific?

My car is working with my old ECU, it's just that I currently have a piston not firing. I'm not "trouble shooting" the spark, I brought it to a mechanic twice and he indicated that there was no signal going to the spark. And the last time he was going to switch out the computer and I thought maybe I could do it myself.

Yes the PCM is from the same model/year/transmission and ECU code.

I don't mind paying for a professional fix the car, but right now I've lost confidence.

Thanks

wmburns · Aug 23, 2010

PCM=ECU.

If the Theft light flashes during cranking it is because the anti-theft system (PATS) has been activated. For the 1999-2004 Model year, PATS disables fuel and spark. This causes a crank with no-start.

More than likely PATS has been activated because the cluster and PCM have not been programmed for each other. In addition, the RFID key codes have to be stored so that the PATS systems "knows" which keys are friendly.

When swapping a PCM from a salvage car, the cluster/PCM will not "know" each other. There are two ways this is normally handled.

A special scan tool is needed to re-program the PATS system to work in it's new home. Normally the dealers is the only one with such tools.

The other is to disable PATS with a hand held programmer such as SCT.

Often when purchasing a replacement PCM from a re-man, it arrives with PATS disabled. The PCM can be swapped and the car driven to the dealer for re-programming.

The salvage yards simply pull the PCM and give it to you. Of course, you could purchase the cluster as well (keep the cluster and PCM together). That saves one step. However, unless you also get the keys from the wreck, the key codes will still not match and still need re-programming.

Some lock Smiths may be able to either re-program PATS or disable PATS. Call around for pricing.

Another option is to use the old PCM to drive to the dealer. Swap it in the drive through. This will save the cost of a tow.

FWIIW, the V6 Mustang uses a coil pack. The coil pack uses a waste spark set up and as such, fires two cylinders at the same time. The other cylinder is on the exhaust stroke so the spark doesn't do anything.

This is important because IT IS NOT POSSIBLE to have a single cylinder with no spark and it be a PCM problem. If this were a PCM/spark problem, there has to be two cylinders affected. The ignition cylinder pairing is 1-5, 3-4, and 2-6.

For an ignition issue to affect a single cylinder, it has to be the coil pack itself, or the spark plug wires, or the spark plug itself (or something like a bad valve).

It is possible to have a bad fuel injector PCM driver that affects a single cylinder.

Here's some information about a possible DIY solution.

ForScan ODB2 scanner w ELM327 USB

ForScan ODB2 scanner w ELM327 USB

While working on your car have you ever wanted: to find an ODB2 operational PID value (say fuel pressure or MAF)? How about graph a PID value over time? Or compare multiple PID's over time? Access a bi-directional PCM control such as test a...

www.stangnet.com

lostintexas · Aug 23, 2010

Thanks for all the information. I will call around to see about the Keys.

That is what I was told that 1 piston (no6) was not firing. The coils has been changed, all the wires have been replaced, the plugs have been changed. I'm not sure about the valve.

I'm not really good with cars (a computer on the other hand...) so I'm going off of what the repair shop has said and done up to date.

I just didn't want to spend the 800$ on top of what I've already spent because my gut says it's not the computer (but again I'm not mechanically inclined).

wmburns said:
PCM=ECU.

This is important because IT IS NOT POSSIBLE to have a single cylinder with no spark and it be a PCM problem. If this were a PCM/spark problem, there has to be two cylinders affected. The ignition cylinder pairing is 1-5, 3-4, and 2-6.

For an ignition issue to affect a single cylinder, it has to be the coil pack itself, or the spark plug wires, or the spark plug itself (or something like a bad valve).

It is possible to have a bad fuel injector PCM driver that affects a single cylinder.

lostintexas · Aug 24, 2010

Called a local dealer and they said they'd redo the PATS for 100$, so I'm happy with that.

Now if after doing that the car works better I will be ecstatic.

Thanks for your help.

lostintexas · Sep 1, 2010

Well I'm back on the road, I installed the ECU after I got the PATS reprogrammed at the dealership for 138$ plus 28$ for a new key (I was missing a key).

I got all of this done for around 260$ compared to the estimated 800$ from a local shop.

I got my ECU from ebay for 135 including shipping and then the reprogramming.

And most of all the great help of everyone here on the forums for the PATS reprogramming hint.

2002 V6 ECU question

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