ECU Fuse Keeps Blowing after Trackday - No CEL - TT

[JimmyK]

TL;DR:

The 15A fuse (Fuse 50) that powers the ECU and other things repeatedly blows within a few mins of driving, but once replaced (stupid, I know), the car can idle perpetually without blowing the fuse, even if you up the revs to >4000 RPM. No CEL or BCM issue reported by the car.

The car was running hot on the track as expected when the fuse popped. After I found it and replaced it, the car ran for ~10 mins on the track before blowing again, when I decided to tow it. After a couple more fuses to get it off the track property for the tow and to get it to my garage, it seems like the runtime is ~2 mins before it blows, but I didn't want to keep testing to avoid damaging something. Turned off AC, radio, S-Mode, and anything else I could find before the last two fuse blowouts, so less likely that they're culprits.

Also, I'm going to put a bit more info than needed here for someone's sake in the future.

Tests Performed or Planned:

Did some mild continuity and grounding electrical checks with a DMM and a radio electrical fault finder to no avail, all harnesses seem okay to the components listed except the few I could not get to. Used an OBD monitor w/ an experimental CONSULT function to view live data while idling or w/ ignition on.

• Condenser
  - Harness under the Intake Manifold, so couldn't shake or inspect.
  - AC is off during event.
  
• Ignition Coil 1
  - No tests performed since car idles and revs well, no CELs.
  
• Ignition Coil 2
  - No tests performed since car idles and revs well, no CELs.
  
• Ignition Coil 3
  - No tests performed since car idles and revs well, no CELs.
  
• Ignition Coil 4
  - No tests performed since car idles and revs well, no CELs.
  
• Ignition Coil 5
  - No tests performed since car idles and revs well, no CELs.
  
• Ignition Coil 6
  - No tests performed since car idles and revs well, no CELs.
  
• Intake Valve Timing Control Solenoid Valve Bank 1
  - Violently shook cables while idling.
  
• Intake Valve Timing Control Solenoid Valve Bank 2
  - Violently shook cables while idling.
  
• EVAP Canister Vent Control Valve
  - Harness looks okay, will disconnect and test continuity.
  - OBD reads but no changes, possibly since the pressure isn't changing at idle without sloshing, etc.
  
• VVEL Control Module
  - VVEL position sensors and angle advance seem to be working w/OBD monitor, since they change values on idle/throttle.
  
• EVAP Canister Purge Volume Control Solenoid Valve
  - OBD reads % changes under throttle ups in idle that make some sense.
  - Electrical continuity of positive to ECU is good (Pin 21 on ECU), no shorts to ground of ECU or car.
  
• MAF Bank 1
  - Readings look okay in OBD.
  - Plan to check electrically per FSM.
  - Violently shook cables while idling.
  
• MAF Bank 2
  - Readings look okay in OBD.
  - Plan to check electrically per FSM.
  - Violently shook cables while idling.
  
• Input Speed Sensor (for S-Mode)
  - No tests done or planned, located on transmission.
  
• Crankshaft Position Sensor (not listed above)
  - Cables look frayed.
  - Violently shook cables while idling.
  - Electrical continuity of positive to ECU. No shorts to power from supply or sensor line, and no shorts to car or ECU ground.

Components Powered by Fuse 50:

Connector E5 (IPDM) Pin 10 (Unknown Color, will update if checked)

• Unlisted in PCS or EC FSM docs, untested, not inspected yet, no known connection.

Connector E7 (IPDM) Pin 49 (BG - Beige)

• VVEL Control Module [E7 Pin 49] -> [E15 Pin 8]
• ECM [E7 Pin 49] -> [E106] -> [M6] -> [M107 Pin 125]
• EVAP Canister Purge Volume Control Solenoid Valve [E7 Pin 49] -> [E106] -> [M6] -> [M116] -> [F103] -> [F7 Pin 1]
• MAF Bank 1 [E7 Pin 49] -> [E106] -> [M6] -> [M116] -> [F103] -> [F31 Pin 5]
• MAF Bank 2 [E7 Pin 49] -> [E106] -> [M6] -> [M116] -> [F103] -> [F42 Pin 5]
• Input Speed Sensor (for S-Mode) [E7 Pin 49] -> [E106] -> [M6] -> [M116] -> [F103] -> [F58 Pin 1]

Connector E7 (IPDM) Pin 53 (W - White)

• Condenser [E7 Pin 53] -> [E3] -> [F1] -> [F8 Pin 1]
• Ignition Coil 1 [E7 Pin 53] -> [E3] -> [F1] -> [F11 Pin 3]
• Ignition Coil 2 [E7 Pin 53] -> [E3] -> [F1] -> [F12 Pin 3]
• Ignition Coil 3 [E7 Pin 53] -> [E3] -> [F1] -> [F13 Pin 3]
• Ignition Coil 4 [E7 Pin 53] -> [E3] -> [F1] -> [F14 Pin 3]
• Ignition Coil 5 [E7 Pin 53] -> [E3] -> [F1] -> [F15 Pin 3]
• Ignition Coil 6 [E7 Pin 53] -> [E3] -> [F1] -> [F16 Pin 3]
• Intake Valve Timing Control Solenoid Valve Bank 1 [E7 Pin 53] -> [E3] -> [F1] -> [F28 Pin 2]
• Intake Valve Timing Control Solenoid Valve Bank 2 [E7 Pin 53] -> [E3] -> [F1] -> [F29 Pin 2]
• EVAP Canister Vent Control Valve [E7 Pin 53] -> [E3] -> [F1] -> [F103] -> [M116] -> [M7] -> [B1] -> [B31 Pin 1]

Connector E7 (IPDM) Pin 55 (SB - Sky Blue)

• ECM Power Supply

Connector E7 (IPDM) Pin 69 (BR - Brown?)

• ECM Relay Control

Connector E7 (IPDM) Pin 70 (BG - Beige)

• Throttle Control Motor Relay Control

Request

Please recommend any tests, ask for test results, suggest issues, etc. I'll also be sure to update the page once it gets solved, be it by me or my mechanic. I'm avoiding the obvious ECU swap since it works well when idling, and also I don't want to have to deal with re-tunes.

Anything will help! Going to tow the car to the shop that put the mods in soon, but figured I'd try as much as I could with my time off during the holidays. I did try a dealership in case they had some better diag tools, but they couldn't figure it out (and didn't charge me) since it was "too modified" for them, whatever that means .

Reference Information

FSM Pages:

• Power Supply & Grounding - PG-7/8/23 (Shows Fuse 50 relative to Power & Grounding and Harnessing)
• Power Control System - PCS-26 (Harness diagram shows additional Fuse 50 connections rel to IPDM)
• Engine Control System - ECS-XX (Lots of harness diagrams show this connection)

Car Details:

• 2014 370Z Base - 29XXX miles
• Fast Intentions GT2860 RS Complete TT Kit
• TurboSmart E Boost 2 Controller
• Zeitronix ECA-2
• (Can add more, lmk what you want!)