Aloha! I have an 01 B300 w/ford all over it. any way im thinking my PCM is bad. PCM says ECS not working and misfire #4. From what I understand the Gy/Rd wire #359 goes to many sensors and has 5Volts to it. I guessing its feeding power to these sensors? With Key on I have no Volts at the ECS or Pin #91 at the ECU. When testing the Lg/Rd wire at the ECT that goes straight to the PCM I get 2.5Volts ? and with key on. So is Gr/Rd wire #359 needing 5Vs?
Can anyone answer this? there's other odd things going on but I'll start here.

Thanks

 

Ford did use pin 91 as 5volt on some years, but its a pull down circuit so its actually a ground reference FOR 5 Volts
Pin 90 is the 5v

Test any grey/red wire KEY OFF with ohm meter to battery negative, should see 0 ohms of close to it
Turn key on then check grey/red wire with volt meter, to battery negative and then battery positive

If your pin 91 Sig Rtn was a problem you would be getting several OBD2 codes, throttle sensor, MAF sensor, ECT sensor, ACT/IAT sensor codes

Pin 90 Brown wire, 5 volts, runs to throttle sensor and then out to other sensors on the grey/red wire and then back to pin 91
Other sensor use the same 5 volts but as a reference, so EXACT VOLTAGE is not what is used, the difference in voltage between pin 90 and pin 91 is what the computer "sees" from each sensor
Pin 90 might be 5.1v now, and 4.9v tomorrow, and that doesn't matter, because the voltage difference will be the same on pin 91

 

OK but most places I read says the gr/rd wire should be 5volts? I'll ch tomorrow pin 90 for volts Any yes thats why I was wondering why no more codes?
thanks

 

This is from my book for 01 ranger 3.0 pin 90 doesnt to the the TPS ?
still question how do the sensors get power? or is the gr/rd a ground? im ford book just tells the diagrams

 

Yes it does, brown(white) wire straight down to TPS also goes to DPFE sensor

Grey/red comes out of both and to the other sensors

Test the brown wire at TPS, key on, see if it shows 5v

 

OK got it , thanks!!

 

OK Ron,Thanks for the info, Im getting somewhere. I got 5volts on the brown/white wire, so now I'll just try and figure why the ECT isn't getting signal to the PCM. I was wondering why there's wasn't more codes, its starting to make some sense now. Thank you again.

 

Just pulled the ECT as far as I can tell, its working. so why isn't the PCM gettn signal?

 

Use a sewing pin/needle to pierce the green wire on the ECT while its connected, engine off, key on, you should see the voltage in chart below, based on current coolant temp

Chart: https://www.explorerforum.com/forums...jpg?1583516355

So if outside temp is 70degF and engine hasn't been run for a few hours you should see about 3volts on green wire

If engine was just shut off(190degF) you should see under 1 volt, like 0.7 to 0.6volt

The ECT sensors main use is to Choke the engine when its cold, the colder it is the more Choke needs to be applied
Choking means to add more fuel to get more fuel vapor so gasoline engine can start and run when cold
In the Carb days a Choke plate did this, it restricted air flow into the carb which increased vacuum in the carb which SUCKED IN more fuel from the Jets
Fuel injection has the computer adding more fuel when engine is cold based on Temp(ECT)

When coolant gets to about 140degF Choke is usually off, so ECT needs to work but there is a pretty large range of error before it would cause an issue
If engine is hard to start cold and then runs fine after 4 or 5 min, and restarts fine when warm, that could be an ECT issue, it may be showing under 2volts when it 50degF outside, so little or no Choke is applied


Why a Choke is needed
Gasoline CAN NOT be ignited with a spark(spark plug in the gas tank doesn't work, lol)
Only gasoline VAPOR can be ignited with a spark
As most have noticed you can SMELL gasoline more when its warm out, that's because it releases/has more vapor the warmer it gets

A cylinder NEEDS at least 30% gasoline vapor for the spark to ignite it
If cold gasoline is only 15% vapor then you need twice as much to get a cold start
As engine warms up gasoline also gets warmed up in engine bay, so less and less Choke is needed

Quick Start(ether) is often used in colder climates to start gas or diesel engines, that's because Ether is a Vapor at very low temps and can be ignited by a spark, once a cylinder fires a few times the gasoline entering the cylinder warms up pretty fast so can get to that 30% vapor point and engine stays running

 

I do know how a choke works, I grew up in the 60s, and I do understand how and why the ECT works. just when I run a test it says the ECT isnt gettn a signal to the PCM, I'll go and do some test now. oh also that link didn't work but ill look for something

Thanks

 

ok, key on at the green wire from the ECT I got 2.5volts so that means the sensor and connector work? im guessing next I should test that wire at the PCU connection pin 38 to see if it has 2.5volts?

 

Google: Ford ECT chart

2.5v would mean coolant temp is about 90degF, is that correct?

You need to do another test to see if voltage changes when engine is warmed up, 170+ degF, under 1 volt, to see if ECT is working like it should

Yes, you can use a pin in the green wire at PCM to see if its the same voltage

 

Good, this is making sense Heres the way this started, a few months ago the motor was missing and ran like hell. I started checking things and did a compression test. wow, all cylinders below 90 except #4. but it was throwing a code that 4 had a misfire? I pulled the heads and got new ones. went back togeather fine. started it up and it still had a miss, but did run better. ran a test and it said the ECT wasn't working? and the gauge on dash didn't work?

here I am, scratching my head, I did find injector 3 wasn't working properly.

Thanks again, I haven't found anyone that know about this stuff.

 

Ok, engine running for about 15min. test on green wire, 1.35V or 140dg. seems low? also at the radiator tem around 115dg. Low? Im thinking stuck thermostat ?
I'll pull the sensor and check it with boiling water in the house to see if will go to 190dg or so. also im thinking this was the same with both old and new sensors.
stuck thermostat open, im thinking.
Doc

 

Yes, stuck open thermostat

You can feel heater hose and upper rad hose after cold start
Heater hose should warm up with engine, upper rad hose should NOT heat up at all until engine coolant gets above 180degF or so
If both hoses are heating up then thermostat is OPEN

 

Im gettn some where, removed thermostat and got a new one installed. fired motor, with in 5min, my temp gauge on the dash is moving. so yes the thermostat was stuck open. tomorrow I'll try and run a few test on my iPad. I'll be interested if now I have short and long term fuel trim working.

 

just for information here's the car I work on at Bonneville salt flats, this year we broke the record. 307mph and now its The World's Fastest Roadster.

 

VERY sweet ride

 

Now that I have a motor that should be operating some what normal I can start looking at what's wrong with it. To start with I found injector 3 has an issue, not sure what to test yet but I hoping that its the reason I have a miss. I knew it wasn't spark do to other test I did. here's a pic of the fault.

 

I got this thread answered thanks to Ron D. I thiik its time to start a new one for the fuel injector

 

RonD is awesome and extremely helpful and valuable to this community. When I had a misfire on one cylinder, and after troubleshooting and narrowed it down to the injector, I ended up sending the entire set (6) to get them serviced. The one for the misfire cylinder was completely not functioning not spraying. When I received them back with the before and after data sheet and installed them it was night and day difference in how my truck ran. I know you are in Hawaii but there are a couple of Fuel Injection service locations and they offer fast turn around time. You should consider the service.

If you do a search you will see my post under my name that I posted here regarding my misfire and injector. Best of luck, keep us posted of your progress.

 

Thanks, I started a new Thread on the Injector here's the deal, the miss I have has been going on for some time. im sure its not spark, but will go back and check. sense ive started I ended up replacing the heads. the compression was way low. putting everything back together I replaced a lot for the sake of it. plug wires, coil. injectors, not new. etc. it runs a lot better but still has the miss. not until I was able to run a test on the injectors did know the #3 failed. because its a different injector in the motor now im going to check the wiring. I can put another injector in but im guessing I would do the same. yes im in Hawaii. on Molokai so if needed I would have to send the to Honolulu or Maul? But before I do that I'll see if check the wiring. Let me know if you got any ideas