LLY Ficm

[kidturbo]

here's a more properly drawn up schematic of the LLY FICM. fixed the error of the boost converter mosfet too

View attachment 117569

They might have changed it on the LLY, but the LB7 definitely has split ground planes. When testing the one on bench with a bad solder joint, only half the board was powering up. So it's interesting if they changed to single power and ground points.

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[kidturbo]

It also looks like this chip is the one receiving the control signals from the ECM and turns on the injector mosfets

View attachment 117571

AMIS-30421

5v stepper motor controller. Sounds right, fast response. Used on both lly and lb7 models. It's likely a keeper unless something better exists now.



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[DAVe3283]

There are really good dedicated boost converter ICs now with integrated FETs that I'd recommend for new designs. Likely get less ripple and no need for a microcontroller to run things. Still have an enable pin if we had to shut it down for whatever reason.

But I suppose given the voltage conversion doesn't appear to be a failure point, why mess with success?

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[2004LB7]

Uh oh, I broke it

During some testing on my truck. I pulled the crank signal wire pin C2-94 on the FICM to see what it will do. Expecting it not to start as reported before. But after reinserting the terminal back into the connector it still won't start. Getting code P0370 timing reference high resolution signal A. If I clear it it returns when cranking. Disconnecting the batteries didn't help

Verified good connection with the board. Continuity from the wire to the terminal on the board so I know it's inserted properly. Still getting a crank signal on the wire per my scope when it's turning over/cranking

Tried another known good FICM and same issue.

 

[DAVe3283]

DTC P0370 or P0374
Circuit Description

The engine control module (ECM) replicates the signal received from the crankshaft position (CKP) sensor. This signal is sent to the fuel injection control module (FICM) through the engine speed signal circuit. The FICM uses this replicated signal to generate injection current and control the recharge of the fuel injection high voltage circuits. When cranking, the FICM has full control of the fuel injectors. The only input the FICM uses at this time is the engine speed signal from the ECM. The FICM monitors the signal along with the injection request signals from the ECM after the engine is running. If there is a problem with this signal, a DTC could set.
DTC Descriptors

This diagnostic procedure supports the following DTCs:
• DTC P0370 High Resolution Circuit
• DTC P0374 High Resolution System Performance
Conditions for Running the DTC

The engine is cranking or running.
Conditions for Setting the DTC
• The FICM does not receive a crank signal, but does receive injection requests from the ECM.
OR
• The FICM receives an invalid crank signal from the ECM.
Action Taken When the DTC Sets
• The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
• The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
Conditions for Clearing the MIL/DTC
• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
• Clear the MIL and the DTC with a scan tool.
Diagnostic Aids

A missing high resolution signal will cause a no-start condition. High resistance in the position sensor low reference circuit may cause this DTC to set. If the condition is intermittent, refer to Intermittent Conditions .

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[DAVe3283]

My takeaway from the GM diagnostic is check the low reference (ground) for the crank signal, not just the crank signal itself. Maybe that pin backed out? Hopefully it's that simple!

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[2004LB7]

I've re-verified that I have good (replicated) crank signal to the FICM. Both the wire and inside the board. I've confirmed that both grounds to the board are good. Checked them at the connector terminals and on the board once they were plugged in. The wiring diagrams don't show any specific ground for the crank signal. Just a single wire from the ECM to the FICM. So I assume it uses the two main grounds to the board

Still no luck

Also hooked up my laptop and fired up the scan tool. Checked the fuel pressure and getting about 5k psi which is very close to command. Crank and cam missed pulses are zero.

It does show main injection mm3 while cranking showing that the ECM is at least trying.

 

[2004LB7]

screenshot of the crank signal taken on the FICM board while cranking. doesn't look out of place or wrong to me

 

[1FastBrick]

Uh oh, I broke it

Well, That didn't take long...

 

[kidturbo]

Back in cell svc. Verify pin is in all the way and locked by Seconday. I've done it a dozen times. Think it's in, then when ya insert lock, it pushes it out and won't make contact with pin. But looks good to the eye.. Best I got at the moment.

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[1FastBrick]

DTC P0370 test procedure.

Tests/Procedures:

1. Run a redundant wire for the engine speed signal from the ECM pin 63 in the 73 cavity Black connector to the Fuel Injection Control Module (FICM), pin 94 Lt Blue wire. 2. If the engine now starts and runs, make the redundant wire permanent. 3. If the engine still does not start, backprobe the Lt Blue wire at pin 94 of the FICM. The signal should have a 0-12 V square wave pulse and the frequency, (Hz), should match engine RPM. Such as: cranking RPM of 200 RPM should equal 200 Hz from the engine speed signal. 4. Test the Fuel Injection Control Module (FICM) power/ground level with a Digital Volt Ohm Meter (DVOM), backprobing at the FICM. 5. The power feeds are Pink wires, pins 5 and 119. 6. The grounds are Black/Green pin 2 and Black/Yellow pin 114.

 

[1FastBrick]

Back in cell svc. Verify pin is in all the way and locked by Seconday. I've done it a dozen times. Think it's in, then when ya insert lock, it pushes it out and won't make contact with pin. But looks good to the eye.. Best I got at the moment.

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I literally just got off the phone with him and told him about that and the conversation You and I just had about the locks and pins.

 

[2004LB7]

She lives! both of you were right. pin was in the wrong hole. checked it probably a dozen times but was blind to the obvious. a second set of long distance eyes was able to see what I didn't. thanks again guys

 

[1FastBrick]

She lives! both of you were right. pin was in the wrong hole. checked it probably a dozen times but was blind to the obvious. a second set of long distance eyes was able to see what I didn't. thanks again guys

I'm just glad we don't have to scrap it for parts... I mean you did just buy it...

 

[kidturbo]

Now that ya know which pin it is, can ya map out what chip it goes to please??

I think it's important.



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[2004LB7]

Now that ya know which pin it is, can ya map out what chip it goes to please??

I think it's important.



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I'll try but it looks like it runs between the layers. It will be a tricky one

 

[2004LB7]

More information. The crank signal seems to run to pin 32 of the bosch chip on the bottom corner of the board. It goes through a 10k ohm resistor and a 0.4nF capacitor before connecting to the pin


This is the best datasheet I could find for it. Not sure if it's correct

https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.bosch-semiconductors.com/media/automotive_systems_ics/pdf_1/ic_engine_management/bosch_ic_cy320.pdf&ved=2ahUKEwiR_vq5q5-BAxWoO0QIHd5IC_wQFnoECA8QAQ&usg=AOvVaw3d444xcvsS4EC1Z-zDa01O

Per that datasheet. It looks like pin 32 is part of a group of programmable(?) Pins for inputs and outputs. But also looks like it's supposed to be a signal output.

A little snippet from the datasheet on its description:

CY320 is a highly integrated power circuit, designed for supply signal processors and motor management controllers. Serial interfaces for internal (SPI) and external (CAN,
ISO) communication management are integrated.

And a pin list



Wasn't able to find the crank signal pin going anywhere else. But I'll keep looking

 

[kidturbo]

Did ya happen to notice if our yellow and green CANbus wires also run directly to that chip?

I didn't spot any other CAN transceivers jumping out at me on back side of the board while reviewing it. So am guessing they are also using that chip for comms to ECM, via SPI over to our main processor. I just started using SPI to communicate with an 5V ADC chip in latest design, because while processor has ADC built in, it's only a 3.3v chip.

On my NXP M4 based boards I connect TD RD lines through an ISO1050 galvanically isolated CAN transceiver because it's NMEA standard designed to protect other nodes from high voltage spikes on one node, taking down a whole ships canbus network. But noticed that's not common practice in auto industry hardware, especially 20yrs ago.

Also noticed that same chip is doing ISO1941, which is K-Line protocol... So guess where I am focusing today's hacking..

As @DAVe3283 mentioned above, there are several new processrs out there nowadays which can do the job of like 4 or more IC's on here. The STM32 comes to mind. However I'm not the guy to name the best processor for this task. I run LPC/NXP but the coding libraries and compiler isn't a preferred tool for today's cool techie kids.. So anyone feel free to please chime about what's hot [and available] out there today. Looks like we could probably run this whole deal with a Teensy board for prototyping.

 

[DAVe3283]

I'm partial to the teensy myself, but it isn't rated for the temps we'd need for production units. The ST stuff is pretty good, and I used to do a lot with Microchip but their software stack has become really subpar by today's standards.

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[TheBac]

You guys shouldve seen my son thinking about this today. He said he shouldnt have any problem making a board, was planning chipsets and which mosfets would be proper to use. He said he knows people at Bosch and will reach out to them to see if he can find any info on layouts, parts spec and coding.

He kept bouncing ideas off me, and I kept telling him it was above my pay grade. Ken, Jason....thanks for sending him the info.