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Discussion Starter #1
ok I guess this is a cross post as I jumped onto someone else’s post, the. Later realized it was under a Duratec forum.

(2001 ZX3, Zetec/ MTX 75), I have intermittent no start, no crank issues, left me stranded 3x in the last 2 weeks, now no communication between dash & computer = odometer all dashes!!

I swapped out zetec motor August of 2019 after sliding thru a huge puddle & locking up old motor (cold air intake behind front bumper sucked in water), My ZX3 has ~184K, new Zetec was 89k when installed (about 3 k ago).
Alternator is new, Starter is new, new battery cables & all new sensors on new motor (with the exception of O2 sensors), + new DUI Coil pack, 8mm wires, & Bosch plugs. Replaced almost all of the sensor pigtails with the new motor, + made a different cold air intake that draws air from behind the battery.

2 weeks ago running errands one afternoon in 110+ heat, my Focus started running a little hot stopped in traffic but cooled down once moving again, my 3rd stop was for dog food, came out NO CRANK, NO START, ugh!, checked all connections grounds etc. I have checked & rechecked all grounds many times, removed PCM, reinstalled PCM, changed batteries (had one in the back as I thought this was part of me problem), nothing works!? Called my wife got a ride home & came back with my care trailer.

So a week later I'm checking fuses, relays, connections, all grounds, (all ground on body are to bare metal), I find front O2 sensor melted to header, break melted connector apart, order new pig tail, & both O2 sensors + new CAT (have not installed yet) somewhere through this process I lost communication between the PCM & dash?? All relays appears to be fine, fuses good, I pulled the starter its great (new), reinstalled, motor turns over fine if you put 12v to the grey wire next to distributor.

I'm at a total loss?, what have I missed??

Everything else in the car works as it should but there is no communication between the computer & the dash so no start no crank.

Could the PATS be part of the issue??
 

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Discussion Starter #4
The security light (PATS) above the hazard flasher switch flashes every two seconds regardless of key in/out or on.
Hence no communication between Dash & PCM

I may have found the problem, I pulled the PCM to get the #'s off of it & inspect it, here is what I found:
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sounds like either your cluster or your ecu crapped out

plug in an obd2 reader and see if its throwing any codes first

if the code read communicates with the ecu then that means either the cluster is bad or theres a connection issue. Theres only 2 wires that run from the ecu to the cluster.

If you can read codes then your best bet is to just send the ecu off to get theft disabled . If you dont have a code reader and the ecu is bad it would be identified during flashing when you send it in. If the vehicle runs afterward then you know the cluster and/or wiring is bad and you can simply go to your local yard and swap out the cluster first as its much easier than tracing out the wires through the dash. Or just run two new wires.
 

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Discussion Starter #7
I installed brand new battery for staters then started check things again with the power probe.
I have an OBD2 scanner (actually a few), there is power to the OBD2 connector but the scanner (all 3) is unable to make a connection with the ecu?!, just like the dash? It has to be the same wire/wires. On the OBD2 port itself I get resistance on pins 2, 10, 13, ground on pins 4 & 5 , power on 16, but nothing from pin 7? (it's a white wire)
307731
 

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Discussion Starter #8
sounds like either your cluster or your ecu crapped out

plug in an obd2 reader and see if its throwing any codes first

if the code read communicates with the ecu then that means either the cluster is bad or theres a connection issue. Theres only 2 wires that run from the ecu to the cluster.

If you can read codes then your best bet is to just send the ecu off to get theft disabled . If you dont have a code reader and the ecu is bad it would be identified during flashing when you send it in. If the vehicle runs afterward then you know the cluster and/or wiring is bad and you can simply go to your local yard and swap out the cluster first as its much easier than tracing out the wires through the dash. Or just run two new wires.
What 2 wires?
 

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Discussion Starter #9
So after studying wire diagrams OBD2 Dash Harness & PCM & what they have in common by chance I came across on two different diagrams that they also all shared a white wire with the O2 sensors, back to the original problem my upstream O2 sensor melted on the exhaust manifold & grounded out, I replaced the O2 sensor pigtail then traced some wires to the battery junction box, I had checked ever fuse more than once. (I also got new glasses yesterday) So I busted out my voltmeter placed it on resistance & started to check a select few fuses the I wrote down #1 Maxi fuse good, #8 good, #9 gooo… wait a second not good!? Upon closer inspection I found the short! I had to take a pic with my phone then enlarge it to see it clearly, but it was probably bad the hole time probably from the O2 sensor grounding on the exhaust. I had looked at it, but didn't see it, I guess all those scratches on my old glasses didn't let me see as clearly as I thought. I swapped the 20 amp Maxi fuse out with fuse from parts car, dash lit up, OBD2 scanner started working, & it started right up!! I still need to replace the upstream O2 sensor itself, but it runs!
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Check F18 (10A) as well - its on the same circuit for upstream O2. The car will run with F18 blown but not with F9 blown.

Never check fuses 'by eye' - use a test light.

Paul
 

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Discussion Starter #11
Check F18 (10A) as well - its on the same circuit for upstream O2. The car will run with F18 blown but not with F9 blown.

Never check fuses 'by eye' - use a test light.

Paul
😵😂 ya, thanks I'll check F18 too
 
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