When the Fan turns off the ECU disconnects.

[crucian]

Just as the title says. Has anyone else have this problem? When my fan turns off the ECU disconnects and then reconnects. This causes my datalogging to stop. It happened with 2.2.5 and now 2.2.6. I have Windows 8. I do not have the Fan control in Smanager activated.

[Hondata]

Check that you have all the grounds (transmission, head and thermostat). Unbolt each end and clean down to the bare metal.

[crucian]

The ground wire splice came loose for the fan causing the fan to stop working. I corrected that issue, but didn't have time to see if maybe that could have been the cause. I'll check it tomorrow along with your advice to see if I can get the problem fixed.

[crucian]

Still having the issue after fixing the fan. I'll hit up all grounds again this weekend.

[crucian]

Cleaned up all grounds. Added additional grounds. Still having problem. Any other suggestions?

[Spunkster]

What vehicle is this in and what exactly has been done to it.

[crucian]

What vehicle is this in and what exactly has been done to it.

2000 Honda Civic Si
Turbo
Hondata S300 Boost
Hondata CPR
SPAL Fan
Zeitronix Wideband Controller
Dual Deatschwerks intank pumps DW300


Note: The Spal fan draws a lot of current when running, but the ECU only disconnects when the fan turns off. The relay that powers the fan is switched on and off by the fuse box fan relay. The main power for the fan runs off a relocated battery jumper post. The ground is on frame; paint sanded off. I'm thinking that there has got to be some type of interference somewhere because the fan circuit does not run through the ECU.

[Spunkster]

The factory harness has it's grounds in the locations they are for very specific reasons, and there is shielded wire throughout the harness to eliminate interference. Any time you modify this you can introduce interference into the system.

[joeb]

Interestingly i have the same problem . I just installed a Spal fan and started having this same issue .
When the fan turns on its ok , but as soon as it turns off my laptop freezes . My prior fan never did this . Increased electrical noise must be the issue here . All grounds are clean and in the proper places . Perhaps a capacitor is needed on the fan .

[crucian]

Thanks for posting. I was doing some troubleshooting today and couldn't get the ecu to disconnect. The following is what I did:

1. Used my Microsoft surface tablet
2. Disconnected the fan from the relay and lowered it on and off manually using its own source of power and ground.
3. Plugged the fan back into the relay and tried it again.

I'm thinking maybe its the laptop and some type of usb issue. I'll try to do some more testing again this weekend and post again.

[Hondata]

With USB disconnects it is always one of three things:
- non resistor spark plugs (check and replace)
- laptop chargers than create current loops through the USB cable (run on battery and see if it still occurs)
- bad engine / chassis grounds paths

The last is the most difficult to track down. Clean all the metal under the ground straps, then use a multimeter between the voltage between the battery negative and the nominal ground of sensors / relays etc (it should be 0V). In your case, see if ground side of the fan is more than 0V when the fan comes on.

[crucian]

With USB disconnects it is always one of three things:
- non resistor spark plugs (check and replace)
- laptop chargers than create current loops through the USB cable (run on battery and see if it still occurs)
- bad engine / chassis grounds paths

The last is the most difficult to track down. Clean all the metal under the ground straps, then use a multimeter between the voltage between the battery negative and the nominal ground of sensors / relays etc (it should be 0V). In your case, see if ground side of the fan is more than 0V when the fan comes on.

1. I have resister plugs.
2. I always run the laptop on battery power. Learned the hard way.

I did resistance tests between different grounds. I'm going to perform the voltage drop tests like u suggested this weekend. One thing I forgot to mention is that my battery is located in the trunk.

[joeb]

With USB disconnects it is always one of three things:
- non resistor spark plugs (check and replace)
- laptop chargers than create current loops through the USB cable (run on battery and see if it still occurs)
- bad engine / chassis grounds paths

The last is the most difficult to track down. Clean all the metal under the ground straps, then use a multimeter between the voltage between the battery negative and the nominal ground of sensors / relays etc (it should be 0V). In your case, see if ground side of the fan is more than 0V when the fan comes on.

My problem must be the 3rd option . Grounds are in the oem spots and seem to be clean . Its rather interesting that swapping fans would cause this issue . Ill recheck and report back .

[crucian]

I never got this issue resolved. The engine actually misfires along with ecu disconnect at the same time. Makes me think that the ecu is intermittently turning off.

[Spunkster]

Have you tried using a stock fan instead? Also have you tried the ECU in a known working vehicle?