Hello all, it's been 5 years time to break down weirdly again.
489 000km 2005 CVPI, stock everything.

A year ago it started failing to start once in a while when I went somewhere. I'd come out of a store after 45 minutes and get a no start. I found if I put a snowbrush on the FPDM (fuel pump driver module) and hammered on it the car would then start.
Eventually it got more frequent. I barely got it home one night with a hesitant idle. So I bought a FPDM and a Fuel cutoff switch off of eBay.
The car had been a no start for 30 days at this point while I waited for the USPS to find Canada on a map. (spoiler, they didn't) They shipped my parts to NY city twice then returned to sender, 28 Days later! ( I was feeling the Rage). Then I had FedEx send it and got it in 3 days. I installed those, while I was in there I found a green pin on the FPCO switch so I changed the connector, which was included in the kit.

Happy, happy,the car started right up! The hesitation was gone! The power was back and a highway cruise was in order. I did some short 2 exit highway runs. It felt great.
So the next night I ran an hour out of town. While I was there I grabbed an A/C recharge kit. Played with that for an hour and went to come home. NO START. I figured I may have disloged a connector. I checked and rechecked. Fiddled with the FPDM and FPCO no effect.
Then all of a sudden it started. Cool, I'm headed home. But not. Left me on the side of the road just before the on ramp. For the next 5 hours I took apart the fuse box, checked every fuse, redid the engine ground from the fire wall ( had an issue with that previously) played with every connector I could wiggle. Finally admitted defeat. Called the tow truck and had him take me home.


Since then I have been edumacating my self on Utube, watching Scanner Danner, MR. DIAGNOSTECH and DiagnoseDan among others. I have done the power tests, purchased and ODBII scanner (and returned it) and have re done every ground I can find on the front end of the car. repaired 7 green wires. Mapped out the fuse box to PCM wires, repaired some twisted in wire wrapped in tape that powered the main ignition switch ( fuse 2 in the underhood fuse box- BJB, 25 amp ) this use to short and blow on occasion (ex-cop cars eh? What ya gonna do?).
I'm at a stand still.

The ECM is intermittent although the (+) side of the power checks out. I have 12 volts at the center connector from fuse 3 in the underhood BJB and less voltage (3-4 volts?) from the line that comes in from fuse 20, 15amp, in the BJB. The sensor lines reads at 4.5 volts and will climb as sensors are unplugged. (Tested at the MASS AIR FLOW sensor.)

Scotty Kilmer came to me in a dream ( or Utube was on an autoplay playlist while I napped ) and told me to unplug one sensor at a time until the ECM comes online. It never did.
While doing this I found the Crank Sensor wire was green so I replaced the pigtail. I returned the ODBII scanner because I had no contact with the ECM. Then went to bed.

Last Thursday the ECM came online, I don't know why, I thought it was the Crank sensor repair I had done a few days previous (Sunday). The Check Engine light came on and it started right up. Ran for 10 minutes then restarted after I turned it off. Right away, no problem. I was of course on my way to work so I tried it when I got home. I had to tuck some stuff away and put the fuse box back in place and it went back to a no start. I checked all the power yet again. (+) good to ECM, no blown fuses. ARGGGGGGGHHHHH!
Then all of a sudden, whilst I had the Fuel Injector relay removed; #203 ( I was playing musical relays, using the horn relay where the ECM was as it had the least hours on it) I turned the key and got the check engine light. I cranked it, remembered the Fuel relay; plugged it in an Viola! Starts. Woo hoo, high 5 myself. Hurt my arm patting myself on my back... For about 5 minutes until it shut off again.

Since then I CLA'd the grounds , checked the (+) power at the ECM, Looked for CEL, closed the hood and walked away...

I have somewhere around 50-60 hours in this. I'm missing something (besides a brain and my sanity) and one of you guys probably are looking at the screen saying "Oh that's easy it's XYZ..."


Recap:
- changed FPDM, FPSO, FPSO connector, fuel rail pressure sensor, cleaned vacuum tubes to sensor as well.

- cleaned main engine to firewall ground

-replaced all 3 (+) positive battery connector and a new marine terminal.

- CLA'd all underhood grounds, including hood ground straps at both ends.

-unplugged every sensor one at a time and checked for CEL light anf ODBII COM

- looked at the wiring harness and unwrapped the passenger side ( why I found main ignition wire broken ) no other broken wires so far.

-no Check Engine Light, no ODBII COM, speedo sits at 40-50km/h but corrects itself when CEL comes back and speedo works fine.

I need complete diagrams (and quite possibly a complete wiring harness with underhood fuse box) for this 2005 CVPI, I also need a diagram with pin outs for the three connectors on the ECM so I can test grounds.
...and if you happen to know what's causing this, for the love of sanity please throw me a bone!


Thanks guys.

PM sent.

Major Clues: found broken wire, corroded wires & connections. No CEL or OBD power (means no battery power to the PCM).

I would swap the PCM diode with another (502 in the BJB (503 is the same I think for horn)). Then I'd chase down that Orange/Black wire that sends Battery power to the PCM, looking for a near-break in that circuit.

It really sounds like a hidden, corroded, almost-broken power wire. You could always try running a jumper wire from the PCM relay to the PCM connector, and see if that works...

One more thing... How's the alternator-to-block contact (grounding) surface?

Here's a link to a wealth of info that just might be of some use:
http://www.supermotors.net/registry/7603/65367-4

dRock96Marquis has been on this forum also, for a very long time.

Fuel Control wiring:
https://www.supermotors.net/registry/media/748938_1

2006/07 Power Distribution: (this might be the one for you!)
https://www.supermotors.net/registry/media/560816_1

It makes sense to spend $ 30 to buy a paper book on Ebay - 2005 FORD CROWN VICTORIA MERCURY GRAND MARQUIS WIRING DIAGRAMS.
Or $ 50 to buy a set with Workshop Manual. Without such documentation, I would not even try to do anything!

Actually, yes + power to PCM is there. Even when no CEL. That's why I am chasing grounds.

On the plus side I now have complete wiring diagrams courtesy of the local shop. Including the location of all the grounds.

I did forget to add I swapped the Horn and ECM diode previously. I've tested so much I've forgotten things. I always have power at the ECM. Just no CEL.

Many thanks for the links.

I'll update when I get back to it.

Don't forget there are two different power uses - the main BATT power and the keep-alive power. If both are there, you're ok. If only the keep-alive power is there, you'll have those symptoms. That's why the necessity for checking power at the PCM pins...:-).

I think there's two, maybe three pins for main power; only one for the keep-alive power. And a number of grounds... :-(.

Make sure to check the main ground from the battery to the bellhousing bolt by the starter, and the alternator to block surface...

Best of luck...

Have you checked to see the battery and charging system are putting out full power? I have gotten loss of comm and several power related codes on my old DeVille. It had a built in scanner with clearing, didn't actually throw an engine light. Turned out to be a cracked battery, it's under the rear seat. Lots of negative temp days and snow up to the belly pan. It would randomly have 0 power then if you hit hard anywhere the vibration would restore full power.

I found when replacing the battery the construction of its OEM batt was best to find. Most have changed overtime which just cuts life some, perfectly safe. They set the alt to charge up to 15.2v because of current draw on those. When built batt design was common that could take the extra. So it had a really quick quick charge if it got drawn down. However it would basically cook many betteries that extra half or so volt. This one did between that and extreme cold right off the ground split.

I can't test it as it won't start; however it did make 14.8 volts last time it ran (last Thursday).



You missed this one. There is OBDII power, just no COM




I have been doing much testing....another 6 hours of probing, poking, cleaning, lubricating and adjusting. Been working on the car too...

Here's what I have found:

I took apart both drivers and passengers kick panels to check the grounds. Pass side A-OK drivers side was Green. Soaked in Evaporust for 90 mins and gave it a good wire brushing as well as a coat of dielectric grease upon re-installation. No effect.

Battery Junction Box fuse 20, is low voltage as previously tested above. This powers the Digital Transmission Range Sensor.(thanks for the diagrams shop guys!)
I have been reading about this sensor. It's known to corrode internally and fail. The pigtail repair connector list's for $50 and seems to be a popular item.
I haven't found definitive anecdotal proof (ha) that it can cause a no start, nor have I found out exactly what the voltage of Fuse 20, BJB should be but I'm gonna guess closer to battery voltage than the 3-4 volts it's showing. Indicating perhaps excessive resistance or a partial shunt to ground.
I'll take off the DTR Sensor connector next time and see what the voltage on BJB Fuse 20 is. Fuse 20 also supplies voltage to the ECM. This may be the intermittent issue of COM/NO COM. I hope to see the Check Engine Light once the DTRS sensor is disconnected.
The DTRS is the one sensor I couldn't reach when I was unplugging them one by one a few weeks back.

I also tested all the grounds in the PCM, all OK, battery voltage from (+) to (-) in the 50 pin connector.

Okay, I acquired a reliable power distribution schematic from this site:
https://www.crownvic.net/drock96marquis/

As I suspected, Fuse 1.3 of the Battery Junction Box (BJB) is for the PCM KeepAlive PoWeR (KAPWR), which simply keeps the computer's RAM memory alive. Fuse 1.20 of the BJB provides PCM VPWR, which is the main operating power for the computer. Fuse 2.20 of the Central Junction Box feeds the Digital Transmission Range Sensor. Same fuse number, different fuse box. I think you got Fuse 1.20 confused with Fuse 2.20.

So, if Fuse 1.20 (BJB) is a low voltage on both sides, you should test the PCM relay input and output for +B voltage, and check F1.7, which feeds the relay input (always hot).

I should add that the 2005 & 06 diagram shows the PCM's VPWR coming into connector C175b pins 35 & 36, a solid Red wire.

The 2006 diagram shows the PCM's KAPWR coming into C175b pin 45, a Rd/Wht wire. They don't carry that much current, so they're small gauge wires.

OK, this is why I shouldn't post at 5:42 am after no sleep.

I sit corrected. Fuse 1.20 in BJB feeds the PCM and the Throttle position sensor. If this is low volted sometimes then have I found my issue?


The problem with this is I get full battery voltage on the two red wires coming into the PCM when last I checked. I have seen 3-4 volts on Fuse 1.20 previously. So intermittent. I still had no Check Engine Light. No start.

So, what would cause low voltage on BJB F1.20? A short/partial short. What bugs me is FULL battery voltage on pins 35/36, good grounds in the same connector and yes Keep alive power from F1.3.
F1.7 is fine as it supplies power to the PCM relay.
Still no Check Engine Light. Crank and no start.


Now, getting back to F2.20 from the inside fuse box.This powers the Transmission DTR Sensor.(again wiring diagrams at 5am ughhh)
There's no voltage on F2.20 unless you are cranking. F2.12 is constant power to the DTR. I'll still check this out as I bought a jack and jack stands to go under the car.
There's the possibility the DTRS is pulling the PCM sensor line down. The Canbus is, as I understand it, a 5 volt COM bus. When I tried unplugging sensors one by one it never got over 4.5 volts. I didn't unplug the DTSR so I'll give that a shot. Fuse confusion notwithstanding.

Thanks for the review and corrections. BTW Yes I am posting at 4:25am but there was some sleep in there this time so thing make more sense.

That voltage on Fuse 1.20 is the same as on Fuse 1.19 which feeds the injectors, and Fuse 1.21 which feeds the control coil side of the AC Compressor relay and the O2 sensors and EGR and EVAP stuff. So if you have low voltage there at the fuse(s), and your PCM has full +B, then ??? Have you checked one of the injector wires or Fuse 19? You might try pulling Fuse 1.21 to maybe eliminate that whole circuit...


Was the PCM connected when you checked?


There's a flat connector on my '06, on the top of the inner fender at the rear of the BJB, that has several wires (5 or 6, maybe) that come from the BJB and go into the main engine harness. Have you cleaned/reseated that connector? And the other two connectors right beside it, just for jollies? On the older cars, one of those provided power to the old relay box on the drivers side fender that held the PCM and fuel pump relays, so maybe...?


Low voltage can also be caused by a very bad connection (corroded blade or almost broken wire, for instance) providing more resistance than the rest of the circuit, thereby causing a voltage drop. This makes me think it's time to open up the BJB and do some serious looking/cleaning with electrical contact cleaner.


Yes, cranking OR in Run..Probably no need to check the DTRS...the engine wouldn't crank if that wiring/system were the problem.


I don't believe the DTRS is connected to the CANBus at all. Do you have a scanner that has LEDs to indicate bus activity? Or have you looked at the voltage level changes when turning the key from OFF to RUN? You should see some level of AC voltage anyway, but the frequency is in the KHz, so AC or DC should read pretty much the same.

One last thing: our two cars still use the J1850-PWM OBDII protocol. Some info:
https://weber.instructure.com/courses/181471/pages/j1850-41-dot-6



No prob! Just remember this if I ever show up at your door seeking refuge from the fires!

Wow. Thursday, I decided to drive to a wrecking yard and get a car computer, 164 miles round trip. Why?
Because, I tested the voltage at the MAF sensor on the air inlet tube,red wire, which is on the same line as the two power inputs for the ECM, center connector, pins 35 & 36, (solid Red wire) 4th row down from top, on the computer. 3.2 -3.4 volts. Unplug center plug from the ECM, voltage jumps up to full-12.6v battery voltage. Plug it back in down to 3.2 volts. I probe over at Fuse 1.20 in the underhood Battery Junction Box. 3.4 volts. Unplug the computer again, full battery voltage.

I decide "Bad computer" look one up on car-part.com. Call the yard verify it's in stock and even the same prefix on the label. ( There are 33(!) computers listed for Crown Vic in 2005. 13 for Police. ) Off I go, drive 4 hours, spend $75 on the ECM, $40 ish on gas. Great. Put it in. SAME DAMNED THING! I was not deterred.

Back to the under hood fuses and relays. Thinking about what we discussed. Fuse 1.7 BJB, sends power to ECM relay 204. I put the meter on Fuse 1.7, get full battery voltage. Fuse box is out of its mount with the bottom cover off so I start wiggling Fuse 1.7 and yellow wire with black stripe. Power drops off to 3 volts. BINGO!
I thought it was something to do with fuse 1.20 being low. Turns out Fuse 1.7 - 4th fuse down on the right hand column in the underhood fuse box - BJB. 30 amp, small fuse, GREEN.
Pull the fuse. It's OK, not blown, no corrosion. HOWEVER. The yellow w/blk power wire running into the bottom of the fuse box is loose. So in one position FULL battery voltage and Check Engine Light, car starts and runs. Wiggle it. voltage drops to 3.4 volts. NO Check Engine Light. No start. The buss bar - voltage supply side to the Fuse 1.7, is loose too in the BJB.

Wish I had found that a day earlier. 142 miles, 4 hours and $105 sooner. Put the original computer back in, wiggle Fuse 1.7 and CEL comes on car starts just fine. While it's running, wiggle Fuse 1.7, car shuts off. Tried it with both computers. Same results.
I took a pick, bent the pins to tighten them on both side of the fuse connector in the holes for F.1.7 in the fuse box inwards to tighten them up. So no longer throwing the fuse blades like a hot dog down a hallway hoping they touch the sides once in a while. Even put a new fuse in there too.

So after being towed home after waiting on the side of the road for 5 hours, 100 plus hours under the hood, 30-40 hours watching Utube diagnostic videos, fixing green wires, replacing the connector on the crank sensor, cleaning 7 green ground wires. Epoxying, Heat shrinking, taping and re-sleeving wires.
$350 + bucks on tools, 200 ish miles drivin for tools and computer (bought a HD floor jack 25 miles outta town) $105 for the computer I can honestly say FORD needs to weather pack their damn fuse box on the back side as well as a better cover too, put some sealant on the ground points and also,

I hate doing wiring!

Now for the guy reading this on his phone on the side of the road. Hope you can tighten those fuse connector pins and save the tow truck charges.

Yeah, "wow" is right. Shame it took so much money and time, but glad you finally got it. Thanks also for the detailed update.