8.1L DBW > DBC Conversion Guidance Needed

[StrokinIt383]

Hello all, first post for me here. Brand new to hptuners and new to tuning so I'm starting from scratch here (please go easy!). I have a 69 Blazer that I've swapped an 8.1L/4l80e into and am in need of some guidance. I've reworked a 5.3/6.0 harness/throttle body and am using the 0411 PCM from a DBW 8.1/4l80e yukon xl.

I have converted the DBW TB to a DBC TB from a 5.3/6.0, wired the IAC/TPS to the PCM. Based on the research I've done, I need to modify ETC to zero, which has been done. Also, as I understand it, this PCM should have the ability to operate the IAC however I have not yet tested it.

PCM details:
0411/P01
OS: 12216125

My questions:
1. How can I, in VCM scanner, test that all sensors are operating properly? TPS/IAC/MAF? Even cam and crank position if its possible.
2. When modifying the ETC to 0, do I need to perform a write entire or calibration?
3. Are there other modifications that must be made in the PCM in order to operate the DBC TB?

When the engine was initially fired, it started just fine. However, it seemed as if something changed a few seconds after starting. Audibly, you could hear a change in the way it was running as if if was making a switch in the PCM (sorry if this is not more clear). Also, the idle was high and slowly rose as time progressed. Unfortunately, the transfer case is out now and I did not have a chance to start and log with the scanner. I will do that soon. With the tune being from a stock 8.1/80e, I thought it would be pretty well spot on. However, it seems that something is off.

Lastly, I understand that much has changed with hptuners over the last 10 years. Much of my searching populated old threads and so I wasnt sure how much is still accurate. Please go easy on me as I'm new to this. More than willing to do the leg work and learn, just need some guidance.

Thanks in advance all.

[1970ss8.1]

I just did a 8.1 DBC in my chevelle. But I?m using a P59. The 0411 is easier to do it, but less ram. In the scanner just log TPS and IAC position and commanded. If you are getting readings from those they are working. My initial go at it was a failure. I had to write a 2004 GTO OS into the pcm and copy over all the tables from the 8.1dbw pcm. The original 8.1 OS was DBW so it wouldn?t drive the IAC but it still read the TPS. I got the IAC to work, but have a lot of tuning to go. My 8.1 is extremely modified and has a Nick Williams DBC 120mm TB.
Upload your tune file and I?ll take a look.
Also a log.

[StrokinIt383]

Ok, better late than never. TPS is working fine it appears. Registers 0>100% when logging (engine off).

That said, it appears I have an issue with O2 sensors. I need to check to see if I accidentally have them reversed. Anything else that could cause this? More to come once I check out the wiring. Log attached.

[StrokinIt383]

Update: Verified wiring to O2 sensors and they are wired correctly. O2 sensors are new. Any ideas why the large discrepancy between bank 1 and bank 2?

Also noticed that I had codes p0342 and p0343. I verified that the cam sensor is wired correctly and cam sensor is new. I cleared the codes and will log again later.

Lastly, when comparing the 8.1 TB to the DBC TB I noticed that the 8.1 did not have an idle air hole in the TB blade while the 5.3 did. I am swapping the blades as this could be causing my high idle issue. IAC not moving at all, TPS at 0% but seems to be getting too much air.

Thoughts? Thanks all

[1970ss8.1]

You need to write an operating system from a vehicle with a factory DBC over the DBW OS.

[1970ss8.1]

I just looked at your file and I was fighting the same issue. Your OS makes the ecu think that you are still a dbw engine. You need to write entire a file from a express van with a 411 and 4l80, then copy over all the tables from your 8.1 tables. It is time consuming and a pain but that made mine work.

[StrokinIt383]

Thanks for the feedback. What makes you think this is the case (not challenging just learning)? I assumed the IAC wasnt moving because the hole the in throttle body was allowing too much air in at idle. I've found a few threads where this same ECU and OS worked with DBC. Does it have no effect when you set ETC = 0?

This weekend I plan to finish up the exhaust and ensure no leaks then rescan to see what the O2's look like. I've swapped the TB blade already and can see what affect this has on IAC and idle RPM. More to come. Thanks again.

[1970ss8.1]

The ECU is requesting IAC counts so it should move. If you dout it put your finger over the hole while it is running. From what I?ve seen the 8.1 os won?t drive the IAC.

[StrokinIt383]

You are correct. I had a spare ECM from 6.0/80e. I swapped it with the 8.1 ECM and the IAC worked and it idled as it should. What tables/areas are necessary to move over from the 8.1 tune? I moved the idle airflow, primary VE and high/low octane tables. What am I missing? Thanks again for the input.

[1970ss8.1]

I copied all tables it would let me

[rkb405]

Anyway you can post the original read from when this was the 8.1/MT1?