I need some help with my LS swap. It will crank but not start and I have a U0100 DTC. I'm hoping this is something others have experience with. Here are the current DTCs (I'm not worried about the EVAP at this point):
0x7EA: U0100 - Lost Communication With ECM/PCM A (Permanent)
0x7E8: P0443 - Evaporative Emission System Purge Control Valve Circuit (SES, Pending, Current, Old, History)
Here's the swap summary:
*Donor engine is Gen 4 LC9 (5.3L) with a 6L80 from the same '11 Silverado 1500 (running a E38 PCM with a PSI conversion harness)
*Vehicle is 2004 Land Rover Discovery 2, with the transfer case retained (so I don't have a GM transfer case control module)
*I'm using the Land Rover to trigger the starter (so the E38 Starter Relay Control is not connected).
*I've turned off the starter diagnostics and set the fuel pump to standard (not the FPCM as I'm using the Land Rover fuel pump).
*I get fuel to the motor and it turns over but no ignition
*I've disabled VATS and did a complete rewrite.
I've attached my latest tune and a log from a recent crank. I'm happy to pay a professional tuner if this is more than a simple issue as I'm fairly new with HP Tuners. Thanks!
Your U0100 is coming from the TCM, not the ECM. The ECM cannot set a code for not being able to communicate with itself. And besides, U0100 is disabled on the ECM side (as it should be). It is enabled (as it should be) on the TCM side.
OS tab: Starter Fault Checks is still enabled.
System tab: General: Starter Relay diag is still enabled.
If you intended these DTC to be disabled, you picked the wrong option. 'No MIL Light' means the tests still run. No Error Reported disables the tests altogether.
P0513 - Incorrect Immobilizer Key
P0615 - Starter Relay Circuit
P0633 - Immobilizer Key Not Programmed
P069E - FPCM Requested MIL
P1631 - Theft Deterrent Signal Not Correct
U0121 - Lost Comm With ABS
U0140 - Lost Comm With BCM
There may be some I overlooked. You need to go back through the DTCs with a very close eye.
You've disabled the post-cat O2 tests, and the post-cat O2 codes, but left the catalyst test enabled.
Do a fresh read of the tune that's in the truck right now, and post that file. Sometimes the file you've written doesn't match the file that makes it into the ECM. Particularly, the VATS status. You did do it with write-entire the first time after changing the VATS, right?
Thanks for the quick response. Yes, I did a write-entire for the VATS (and again when I loaded the latest tune). I went back through the ECM DTCs and found a few more that likely should have been set to no error reported (the no MIL was the stock setting). I also updated the starter parameters.
Here is the tune I uploaded and then downloaded to confirm. Unfortunately, the engine will crank but not start.
Will the P0100 code keep the engine from starting? I can read the TCM tune with HP Tuners so is it possible for HP Tuners to be able to read/write the transmission without having a connection to the TCM?
Not knowing what type of CAN layout PSI used, unfortunately, the only advice I can give there is: you will have to trace the wires out and make sure the right pins are connected where they should be. In effect you will have to draw your own wiring diagram before you can go diagnosing where the problem is. Any tips I might offer, like 'check for 120-ohms between DLC 6 & 14 with the ECM unplugged, but TCM still connected' would be wrong if they used a different circuit design ('wye'/'tee' using three terminating resistors instead of 'inline' with only two resistors) than what was used in the factory wiring harness.
One thing you could try - unplug ECM and attempt to read the tune, see if the TCM still shows up. Then do the reverse, unplug only the TCM and see if the ECM is still there. If the circuit is a 'wye' you will lose only the one module that's unplugged. If it's 'inline' like the factory, unplugging the ECM only makes the ECM go away but unplugging the TCM loses them both, since the TCM is connected as a pass-thru.
I don't know what kind of support PSI offers, but it would be great if they could give you a diagram of how the CAN lines are set up in their harness.
I would say 'no' on whether the U0100 could cause a no-start, but then there are certain ETC faults that can result in an intentional no-start for safety reasons, and parts of the ETC operation are affected by stuff that lives in the TCM.
Just because I'm a complete weirdo and I like a good mystery, I am curious why if there really is a no-comms issue there isn't a corresponding U0101 - No Comm with TCM being set in the ECM.
You still have U codes in the TCM for ABS & BCM that are set to No MIL Light. Catalyst test still enabled.
Thanks again for the response. I am going to give PSI a call tomorrow to see what ideas they have. Oddly, after I updated those U codes in the TCM I turned over the motor and got one or two combustions and I could smell fuel (which was likely the exhaust). So it did command spark at some point, although I'm not sure it is because of any changes to the tune.
The other issue I found was with the VSS. The original Silverado measured the VSS at the transfer case with an external sensor (so X1-71 and X1-72 have the high/low VSS sensor). As I don't have the Chevy TC, the PSI harness uses a replicated TOS wire.
Is there a setting I need to change to have the ECU look for the VSS from the transmission rather than an external sensor? I see Speedo>>Calibration>>Hardware. In that window there is a Vehicle Speed Sensor>>Vehicle Speed Output that is currently disabled. Should that be set to "RepTOS"? Here's what I changed it to.
After some more diagnosing it looks like my fuel pump is going bad (it had pressure earlier this week but didn’t have pressure today). The motor does have spark so it should run once I get the fuel pump sorted.
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