[Solved] O2 Sensor not functioning
The Problem
The AFR reading on the handheld and in the datalog is fixed at 14.7. On a Bosch 17014, this is the reading when no current is flowing from the sensor. I replaced the original sensor with a new Bosch 17014 and still fixed at 14.7.
I submitted a support request to FiTech and after a week have not heard back. I am turning here for some suggestions and maybe a little moral support. All of this kinda makes me miss the simplicity of bolting on a 4150.
The Setup
- New 347 SBF
- Cam: 218/226, 112 LSA
- Vacuum: 10-12 in-Hg @900 rpm
- MSD Ready to run, 14 initial 34 @ 3500 +15 vacuum
- Autolite 3924 resistor spark plugs
- Moroso spiral wound plug wires
- FiTech:
- Powered directly from battery, and ignition+
- Grounded to engine block (0.2 Ohms)
- Tach signal wired to MSD tach out with shielded & grounded wire, routed by itself.
Thanks for helping.
O2 sensor not the issue. The computer is locking up and going to open loop. Usually electrical interference issue. Where is your coil mounted? Is your blue wire shielded?
Grounds recommended: 2ga battery to block, 10ga battery to frame, 10ga battery to body.
Power recommended: pull power directly from battery.
Thank you for the reply, Austin. See below.
- The coil is a Blaster SS mounted to the front of the driver's side head.
- Blue wire is shielded -- it is coaxial guitar wire with a braided shield that is grounded to the block at one end.
- The blue wire is run on the other side of the throttle body, away from the coil wires.
- Power is pulled directly from the battery.
- 0 gauge ground from the battery to the chassis and to the block.
- Resistance to ground at the throttle body is 0.2 ohms.
- There are no fault codes indicated.
- The RPM hunts around a little bit at idle, but only +-20 -- not the super erratic sign of interference.
Do you know if there is a way to test the open loop hypothesis (short of an expensive EMF scope)? Is there an indicator in the log file, or some experiment I can perform?
To help with troubleshooting, I'll attach a couple of pictures I have on hand. I will take close-ups of critical spots in the morning. I am very much looking forward to tuning the FiTech once it is getting all of its signals.
Thank you again.
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I know it is open loop when it locks to 14.7.
Verify coolant temp sensor reading. You could try using the ECU programmer to reload the software.
ECU programmer is at the bottom of your handheld. Make sure to turn key off and power down ECU after programming. You will need to reset all your initial settings again.
The FiTech coolant temp sensor consistently reads about 20 degrees cooler than my dash gauge. I've already ordered an ACDelco replacement. Do you think that would effect the AFR reading?
By ECU programmer do you mean the "Write cal to ECU" option? If so, are you suggesting I reload the "default V8 T198i 30002 20170320a.cal" file or is there a newer baseline I should download?
Nope, further down. You may need to enable it in the display menu.
The CTS usually doesn't cause that issue, but it is very important the sensor is replaced before moving forward.
Solved. Posting here to wrap up the loose ends and possibly benefit someone with a similar issue.
TLDR; One of the .inf files on your ECU is probably corrupt, re-flash your ECU.
- Replaced the temp sensor, didn't effect this issue, but it was nice to not have to compensate for the ~20 degrees.
- Verified the harness at the sensor -- both signal lines and the heater lines were good.
- The alternator had an internal short and was feeding AC current back through the ground circuit. I replaced the alternator, that fixed the implicit parasitic draw, but did not affect the O2 sensor issue.
- The final change was to do what Austin suggested, and was backed up by a FiTech support rep, re-flash the ECU. Voila, the next start began showing AFR data after a few seconds of runtime.
NOTE: I had to flash the ECU twice before I was able to successfully boot the ECU. This is pretty common -- I work with consumer electronics and re-flashing a firmware is often very error prone.
Quote from Lance on July 8, 2019, 10:52 pmSolved. Posting here to wrap up the loose ends and possibly benefit someone with a similar issue.
TLDR; One of the .inf files on your ECU is probably corrupt, re-flash your ECU.
- Replaced the temp sensor, didn't effect this issue, but it was nice to not have to compensate for the ~20 degrees.
- Verified the harness at the sensor -- both signal lines and the heater lines were good.
- The alternator had an internal short and was feeding AC current back through the ground circuit. I replaced the alternator, that fixed the implicit parasitic draw, but did not affect the O2 sensor issue.
- The final change was to do what Austin suggested, and was backed up by a FiTech support rep, re-flash the ECU. Voila, the next start began showing AFR data after a few seconds of runtime.
NOTE: I had to flash the ECU twice before I was able to successfully boot the ECU. This is pretty common -- I work with consumer electronics and re-flashing a firmware is often very error prone.
Thanks for the update. I have been seeing this issue a lot recently. Had heard that Fitech was suggesting a reflash, ECU programmer. Not sure why this has become a common issue in the past few months, but at least it is not a hardware problem.