Bad ECM?

**Cody Adams** · 12-15-2023

So, to start.

I rebuilt the head after driving for one week, and this started happening.

Cluster lights pulse, AC cluster flashes, and truck lopes are sequenced with the pulse.

When I use the window switches, it speeds up and intensifies the pulses.

So, the passenger battery was removed simply because the truck was just a race truck.

1st new battery stamped 2/23, same result.

2nd new battery stamped 4/23, same result.

Both batteries were sitting on a charger fully charged, good batteries.

They replaced terminals with fresh ones to ensure no cracking in the lead.

0 gauge true copper cable from alternator to battery.

0 gauge to TIPM.

0 gauge to chassis.

Brand new Mechman 240amp alternator, same result.

Is there a way to test the ecm without sending it out?

No codes, nothing.

I am using a pretty nice Launch Scan tool.

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**AK Bob** · 12-16-2023

I recommend monitoring the CAN signal at the DLC with an oscilloscope on pins 6 & 14.

This way, you can see if the signals look okay and if there are any glitches.

If the CAN signal is glitching, disconnect the star connectors one at a time to isolate the issue.

Regarding testing the ECM without sending it out, the only checks you can perform are verifying all the powers and grounds at the ECM.

I would start with the CAN signal monitoring first, attached are a couple of videos that will explain process in more detail.

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