Engine dies, code 1233

[rattle_snake]

Having issue with fuel system it appears. Stock fuel system, pumps, BAP. Car shuts off randomly. Pulled code 1233 for FPDM. First time issue happened, I let it sit an hour then it started and ran a few miles. Last trip ended up with a tow.
30A Fuse to BAP relay was popped, replaced. Relay is OK. BAP has 17 V output, so seems OK. Car will start and run but dies within a minute or two. Monitoring fuel pressure thru OBD, it is erratic. If it drops too low the engine dies. It will restart. Can hear pumps prime and run.
Are these symptoms of 18 yr old FPDM? that has been on higher voltage? Next steps?

 

[01yellercobra]

I'd suspect the BAP before the FPDM.

 

[03' White Snake]

Is your BAP wired before or after the FPDM?

Some cars act funny if the BAP is wired after the FPDM. (This is how KB says to wire it BTW). I would wire it before the FPDM and see if it fixes your issue.

 

[rattle_snake]

BAP wired in before the FPDM and is set to static value (max, 17 V). Looking back I installed 10 years ago.
I can instrument volt meter into bap output and see if voltage fluctuates when fuel pressure does.

 

[rattle_snake]

BAP appears to output 17.28 volts at all times. I don't see fluctuation in voltage when RPM surges or engine dies.
Next was to measure the FPDM output (pump voltage) and monitor with fuel pressure. These are interrelated as that is the control loop. I see pump voltage drop to 7v or lower when engine stumbles, and fuel pressure drops.
Guess it could be FPRS seeing spike and reducing pump voltage but my setup is too slow to see it.
Perhaps the FPDM is resetting, then coming back online sometimes (stumble), sometime not (engine dies). Hence the error code.

 

[rattle_snake]

Is the cobra FPDM different than a GT, or all the same?

 

[Vinnie_B]

P1233 - Fuel System Disabled or Offline

• The PCM monitors the fuel pump monitor (FPM) circuit from the fuel pump driver module (FPDM). With the key on, the FPDM continuously sends a duty cycle signal to the PCM through the FPM circuit. The test fails if the PCM stops receiving the duty cycle signal.

POSSIBLE CAUSES:

• Inertia fuel shutoff (IFS) switch needs to be reset
• Open FPDM ground circuit
• Open circuit to FPDM PWR RLY
• Open FPDM PWR circuit
• Open or shorted FPM circuit (engine should start)
• Damaged IFS switch
• Damaged FPDM PWR RLY
• Damaged FPDM
• Damaged PCM
• Also for Mustang:
• Open B+ circuit to the constant control relay module (CCRM) pin 11
• Open ground to CCRM pin 18
• Damaged CCRM

Diagnostic Aids

The PCM expects to see one of the following duty cycle signals from the FPDM on the FPM circuit: 1) 50% (500 ms on, 500 ms off), all OK. 2) 25% (250 ms on, 750 ms off), FPDM did not receive a fuel pump (FP) duty cycle command from the PCM, or the duty cycle that was received was invalid. 3) 75% (750 ms ON, 250 OFF), the FPDM has detected a fault in the circuits between the FPDM and the fuel pump.

 

[03' White Snake]

Is the cobra FPDM different than a GT, or all the same?

All the same. Same with V6’s.

 

[rattle_snake]

Used SCT to Datalog the fuel related item tonight, idled fine for 10 min or more and didn't have any problem or shut off. Funny how that works. Usually wont run for more than 1. Perhaps cooler temp allows it to run longer before something overheats and reset.

Read code with SCT and it also has 0148 which would make sense from seeing pressure drop out earlier.

FRPS seem OK and reading was stable tonight. pulled vac line, no fuel leak when pump cycled so diaphragm seems OK.

I can bypass BAP easily enough but want to see it fail in datalog first so try that again tomorrow.

 

[rattle_snake]

Try to find time to properly diagnose this issue. Tried to datalog again and couldn't connect SCT after too many attempts....
So I used heat gun to heat FPDM and that made it die. Doesn't like to restart after it fails. So I put FPDM in freezer for a bit, reinstalled and then it started and ran fine. Heated BAP and that didn't seem to matter. Then ran out of time and just ordered a used FPDM on ebay, $50.
So I didn't really positively identify root issue but this shit is dragging on a month now so need to try something. Hate just being a part-changer.

My electrical engineering day job has similar tasks, debugging intermittently failing electronics, and heat is typical cause. OEM automotive failures analysis of motor drivers, power converters, touch controllers. But don't really want to spend my free time on this crap, just enjoying car and doing burnouts.

 

[DSG2003Mach1]

hopefully that's all it is, I've seen several new edge guys have similar symptoms and a replacement fpdm solved it

 

[rattle_snake]

Plugged in the alternate FPDM and problem still exists. Ran for 10 min then died and doesn't want to restart. fuel pump primes but reads no fuel pressure. Re-checked BAP power when in failure condition the BAP output is solid at 17 v. Fuel pump voltage and pressure are erratic if it starts.

I'm assuming that the problem is related fuel control loop, so that leaves only 2 other things, FPS and ECU.

I installed a mechanical fuel pressure gauge on fuel rail and then couldn't get car to exhibit problem. pressure was consistent on mech gauge and reading over OBD. Given this is a diagram type analog sensor, I wouldn't expect erratic behavior.

Reading FPS type threads, I see some about failures after hitting rev limiter. I had floor mat get stuck under gas pedal and hit limiter on 1-2 shift, I shut off engine quickly. Car ran fine for awhile after this event. No fuel is leaking out of FPS boost ref line. Perhaps related?? Throw a new sensor at it?

 

[Vinnie_B]

Hey @rattle_snake you have a electrical issue somewhere in FDPM/CCRM or the FPM circuits as I described in #7

• Open FPDM ground circuit
• Open circuit to FPDM PWR RLY
• Open FPDM PWR circuit
• Open or shorted FPM circuit (engine should start)
• Possible Damaged IFS switch
• Possible Damaged FPDM PWR RLY
• Open B+ circuit to the constant control relay module (CCRM) pin 11
• Open ground to CCRM pin 18

It also possible but needs to be ruled out after the above testing is confirmed.

• Damaged PCM

*This is going to take extensive testing!!


Lightning fastElectrical Automotive Repair LLC (Professsional, quality and honest business is my top priorty)

 

[rattle_snake]

Hey @Vinnie_B,
yes I agree, have checked off some of those items. Somewhere, intermittently is the key.
The blown 30A fuse on BAP/FPDM circuit must be a key though. That one has me stumped.
With BAP the CCRM just drives relay, and all that is OK up to FPDM, which after A/B swap is not issue. Possible communication wires (FPM?) are damaged but unlikely. Haven't tried inertia switch yet...

So have to find time to go through the rest.

 

[Vinnie_B]

Hey @Vinnie_B,
yes I agree, have checked off some of those items. Somewhere, intermittently is the key.
The blown 30A fuse on BAP/FPDM circuit must be a key though. That one has me stumped.
With BAP the CCRM just drives relay, and all that is OK up to FPDM, which after A/B swap is not issue. Possible communication wires (FPM?) are damaged but unlikely. Haven't tried inertia switch yet...

So have to find time to go through the rest.

Hey @rattle_snake. I took a look at this issue, its just a matter of isolating it in the above post in #13.This issue aint no easy fix so just take your time you'll get it. There is no issue in the communication wires that I could see. If you know of anybody who can scan your car using Ford IDS I highly recommend it, anybody remotely experienced using it can diagnose this issue in less than 1.5 hours by checking all your modules and components to help narrow down the trouble circuit which at that point a DMM would finish the diagnostic testing by checking for resistance, opens and shorts in the wiring in between your components. If you cant get the help or answers you need dont hesitate to hit me up. Good Luck Buddy!

 

[rattle_snake]

Ok Thanks Vinnie.

Did some more testing. Let car run until it died. Observed the mechanical gauge vs what is reported over OBD. They appear to correlate. Upon attempts to restart, I see huge swings from 0 to 100 psi as engine stumbles and dies. Eventually it restarted and ran for 15 min without issue. I shut it down and read codes, only one present is P0193. I had cleared codes some time ago.

P0193 - Fuel Rail Pressure Sensor Circuit High Input

Not sure if this code will set when fuel pressure really does exceed 100 PSI.
If sensor output hiccups it causes control loop to go unstable. It appears that FPRS is ok most of the time. Next step is measure raw sensor voltage or try to data log to capture the event.

 

[Vinnie_B]

Ok Thanks Vinnie.

Did some more testing. Let car run until it died. Observed the mechanical gauge vs what is reported over OBD. They appear to correlate. Upon attempts to restart, I see huge swings from 0 to 100 psi as engine stumbles and dies. Eventually it restarted and ran for 15 min without issue. I shut it down and read codes, only one present is P0193. I had cleared codes some time ago.

P0193 - Fuel Rail Pressure Sensor Circuit High Input

Not sure if this code will set when fuel pressure really does exceed 100 PSI.
If sensor output hiccups it causes control loop to go unstable. It appears that FPRS is ok most of the time. Next step is measure raw sensor voltage or try to data log to capture the event.

Keep us posted @rattle_snake you'll get this!

 

[rattle_snake]

I think I found issue, FRPS

Did datalog and fuel pressure correlates to mech gauge. commanded DC adjusts as expected. I don't see anything wrong with log that indicates a problem to fix.

The fuel rail pressure spikes beat the crap out of my cheap test gauge and broke the needle off. Damn it. So I put a volt meter on raw output and placed it on dash to monitor. 0.20 v at 40 psi. hmmm.

So then built a datalog cable with voltage level shifters for SCT3 to log BAP output and FPDM output but couldn't get car to start at all. Fills garage with fuel fumes from exhaust. Pulled connecter off FRPS and tried to start, then plugged back in. FRPS now reading 2.8v and it started. Then proceeded to datalog until it died (850 seconds). after engine stopped FP read 0 psi on ODB, 0.2 v on meter, but mech gauge read 40. So I have the smoking gun, faulty FRPS. Picked up a new one from Ford today.

Note that fuel pump is not grounded in tank and has 2 wires. + one is just power supply and is constant voltage. the - side is controlled with MOSFET or some switch
and PWM to control voltage/current. So data logging low side is volt drop across FET, but can calculate pump voltage as (supply - switch voltage). Added math to log file and could see pump go to max voltage when FRPS said low pressure, but was actually high and flooded engine. hence smell of fuel while cranking also.

So I have high confidence that this will fix. else I didn't' want to test drive and get another tow.

 

[03' White Snake]

Might be flooded too, hold gas pedal to floor when cranking it. Crank for 15-20 seconds. Let starter rest a few minutes, then start it normal.

 

[rattle_snake]

When in failure mode I tried holding to floor and it would fire but not run. Once output from FRPS was correct it starts fine.

Installed new sensor and made successful test drive. Should be solved...