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Amedee, Mercury Technician
Category: Mercury
Satisfied Customers: 26427
Experience:  ASE certified Technician advanced level specialist. Wisconsin certified emissions state inspector
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97 sable OHC vin U- won't start, cranks well and has fuel,

Customer Question

97 sable OHC vin U- won't start, cranks well and has fuel, but no spark-. The check engine light used to be on all the time as the catalytic converter is faulty-too expensive to replace. The check engine light has been off for about a week and does not come on when cranking. I've checked all the regular fuses. I pulled the crankshaft position sensor and it reads 660 olms, about the same as a new one. The fact that there is no check engine makes me think it is the ECU. Does that seem reasonable and can I replace it myself? Where is it located?
JA: Does the light stay on, or does it blink?
Customer: Check engine light is never on
JA: Are you fixing your Sable yourself? What have you tried so far?
Customer: newly used car has not been well cared for. replaced wires and plugs as they were decrepid. Recntly the battery and starter were replaced and seem very good. Replced the coilpack but don't think it needed it and cleaned and inspected the crankshaft sensor. Wire insulation was brittle, but wires are clean and wrapped to make sure not touching, but could have been before
JA: Anything else you want the mechanic to know before I connect you?
Customer: I'm really not a regular car geek. I just have to do this becuase I am busted
Submitted: 1 year ago.
Category: Mercury
Expert:  Amedee replied 1 year ago.

Hello and welcome! My name isCustomerand can assist you with your question. Are you saying that the engine light does not come on with the key on for a bulb check?

Customer: replied 1 year ago.
no engine light on ever
Expert:  Amedee replied 1 year ago.

Ok, this is the problem. The computer is not awake with the key on so it will not start and run. All powers and grounds must be checked going into the PCM with the key on. This included all powers from all fuses, fusible links and even the ignition switch. If all checks out good, then the PCM has likely failed and will need to be replaced.

Customer: replied 1 year ago.
Can I replace the PCM at home or does it have to be a tech to do it? Where is it located?
Expert:  Amedee replied 1 year ago.

You can replace it yourself.. but I dont think that is the problem. I bet its missing inputs preventing it from powering up.

Customer: replied 1 year ago.
where is it located?
Customer: replied 1 year ago.
something I read said I need toi check the connectors to see if corroaded also
Expert:  Amedee replied 1 year ago.

RH Rear Of Engine Compartment, In Cowl

YES, anything that can prevent power to the PCM needs to be checked.

Customer: replied 1 year ago.
sorry I don't know what a cowl is in an engine
Expert:  Amedee replied 1 year ago.

The firewall

Customer: replied 1 year ago.
I see it. There are 2 bolts that hold it to the fire wall and one that seem to be holding the wires on.
I want to make sure I understand before I loose you and don't know how to get you back. I only do this myself as I have a very bad legal problem that keep me broke. I used to work on my old sinple car.
I check the power and ground by pulling the wire conglomerate off the PCM and testing the pins at that point? Is there a diagram or chart for what power and grounds is where?
Expert:  Amedee replied 1 year ago.

YES, I can send you a pinout chart. You need to leave it connector but gain access to the connector and check for powers going into the PCM with the key on. We can even speak on the phone and exhange numbers so we dont lose eachother.

Customer: replied 1 year ago.
please send pinout chart.***@******.***I can't pay the $26 for a phone chat. I am fighting abusive guardianship issues with a corrupt court and lawyers who pound me and others who try to fight the system. I volunteer at a Parkinons school- $60K in debt and no income. I cry at every cent I spend. CHeck out Guardianship: How judegs and lawyer steal your money. A friend of mine wrote it. Don't every get involved in guardian ship.
Don't mean to cry on your shoulder, but back to auto distress. Can you clue me in on how to gain access to the connector without unpluggin it? Sorry I am so dumb on this.
Expert:  Amedee replied 1 year ago.

NO problem. I will try my best. Just gain access to the PCM and connector but dont unplug it. You may have to remove a plastic cover over the back side of the connector. Then from there, using a paper clip, back probe the power wires and check for battery voltage with the key on.

Expert:  Amedee replied 1 year ago.

At the Powertrain Control Module, check for battery voltage on pins 71 and 97 Red wires with the key on. Also check for battery voltage on pin 55 Dark Green/Orange wire at all times. If any of the wires do not have battery voltage, repair as needed and recheck operation.

Expert:  Amedee replied 1 year ago.

Here is the PCM connector pinout chart

Expert:  Amedee replied 1 year ago.

I am glad I can help!

It has been a pleasure working with you. Please dont forget to honor your good faith deposit by rating my answer as "Excellent Service" for assisting you today.

Please let me know if you have any further questions.

Customer: replied 1 year ago.
Any suggestions/cautions for installing another PCM? It will arrive in a few days.I could not get even a small safety pin into the pin hole as the wire fills the hole. I tried shoving one in there and checked for continuity on hte back side and I was not connected at all.
Since I can't test any connections I have purchased an eBay PCM hoping that will solve the problem before I have to have it towed and finance the repair.
Expert:  Amedee replied 1 year ago.

I would encourage you to check the inputs to the PCM before replacing it.

Customer: replied 1 year ago.
I can't get at the inputs. For $30 I can get a different PCM. Then I will know if it was faulty.
If I find a faulty input I won't know what to do anyway. If it's not the PCM I'm going to have to have someone else fix it anywaySo when I put in the new one what do I need to know?
Customer: replied 1 year ago.
My neighbor said I could check for voltage with the connector unplugged from PCM and pins 71,97 (with key) and 55 (all the time) checked out with battery voltage.
Expert:  Amedee replied 1 year ago.

YES< you can do that.. but better yet, check them with it plugged in. That is the correct way to check the inputs.

Customer: replied 1 year ago.
i, being a sissy who is forced into getting her fingernails grossed out have no idea how to get any pin or other piece of metal down in the same hole as a fat wire, have a found voltage the wrong way.
Does my info that there is voltage with the connector unplugged give us any usable info?
Customer: replied 1 year ago.
Battery voltage on 71, 97 with key on with connector disconnected from PCM
Battery VOltage on 55 all the time with connector disconnected from PCM
What does this mean?
Expert:  Amedee replied 1 year ago.

Yes ma'am. This means the wiring up to the computer is good. The only other possible cause is if the reference voltage is shorted out. This is a 5 volt reference that goes to the TPS and MAP sensor (and maybe some other sensors). If this voltage is shorted out, it will pull the PCM down causing this problem.

Customer: replied 1 year ago.
if I have 5 volts to TPS and MAP then it is a problem with the PCM and it needs to be replaced?
Expert:  Amedee replied 1 year ago.

Thats correct.

Customer: replied 1 year ago.
MAP--I have 12 volts between A (red) and Battery negative with key on: zero key off
--12 volts between B (black) and Battery positive
--12 volts between C (white) and Battery positiveTPS-- I have 5 volts between top wire (3) and battery negative key on
---12 Volts between lower wire (1) and battery positive key on suggested testing that way
Expert:  Amedee replied 1 year ago.

Hello and sorry for the delay! My mistake. I meant to type MAF sensor. This engine does not have a MAP sensor. However, you did the test correctly. It should have 12 volts on the red wire at the MAF sensor.

There is also the DPFE sensor.. which is the digital pressure feedback EGR sensor. This sensor also gets a 5 volt reference. I would disconnect this sensor and see if the check engine light comes back on with the key on. I suspect it will not because you have 5 volts at the TPS so I dont think the DPFE sensor is shorted out. But it would be worth a try. Of course be sure there is a 5 volt reference going to this sensor with the key on.

If all checks out good, I would suspect a bad PCM.

Customer: replied 1 year ago.
Are there any precautions I need to know about when replacing PCM?Can I just plug it in and start the car?
Expert:  Amedee replied 1 year ago.

This one should be plug and play