ECU Drops out when 02 sensors connected
New user here. I have a ULS 70051 that I bought a while ago. Harness has been on my build for a while, and the ECU was installed recently with power applied for the first time last week.
I went to flash the initial config to the ECU and ended up with the "ECU no response" error.
After getting beyond my aggravation I did some more digging:
- Pulled fuses from the fuse block and through trial and error determined that when the 02 sensors are connected the ECU drops out.
- When the 02 sensors are not plugged in (doesn't matter which side or if only 1 side is plugged in) i am able to flash the ECU and read the sensor outputs on the handheld. I was also able to complete the initial config for my motor with no issues.
- The handheld shows the battery voltage at 10- volts...BUT
- Battery is 12.6
- Voltage at the ECU Relay is 12.5 volts
- Voltage at PIN 31 on the FI Tech ECU connector (Battery Voltage) reads 12.5 volts.
- 0.1 Volt drop doesn't seem out of reason - and 12.5 V should be plenty to operate.
- Grounding is good. I measure 0.01 to 0.02 ohms from any of my ground locations back to the battery negative.
- I have a heavy ground from the block to the battery, 2 grounds from the heads to the chassis, and a heavy ground from the chassis to the battery.
- No electrical issues with any other circuits. Lights / gages / blinkers etc all work fine.
- The 02 sensors aren't blowing their heater fuse. It's not even getting warm.
- The IAC seems to be working - I can hear it changing when i turn the key from off to run.
I called tech support and the guy was...not super helpful but he did issue me an RMA.
I've reached out to FI Tech email support. Will see what they say.
Anyone else experienced this? Any ideas?
Interesting issue. Never seen this. Seems you have done a great job of testing.
The low voltage showing on handheld is concerning. Injectors require approximately 10.5volts to open alone. If you are showing 10 with key one, then the voltage drop during cranking will be well below minimum.
If I had taken your Tech call, the same path would been taken. That system needs to be sent back for testing and repair.
Emailing will not get you a different answer. If anything it can create confusion. That email goes to the Tech department. Same folks you talked to on the phone .
Send it in. Make sure to send ECU, harness, handheld, handheld cable and the O2 sensors.