Erratic Sensor Readings After Ongoing AFR Troubleshooting

[bemmis]

-03 Civic Si
-13.6:1 K24 E85 Skunk2 Ultra 2 cams
-KPro V4
-PND (also PNF)
-KPro bought through King Motorsports, 2017

I am having erratic readings across Battery V, INJ, IGN, TPS, O2. The ECU will not start a known-good vehicle. On the new vehicle, the fuel pump does not prime and seems to have no response to the immobilizer setting.

I have been trying to source running problems with the car for several months. Prior to this year, the car ran normally. No changes had been done to the car besides an engine rebuild, however, the alternator regulator was damaged in the process, and the ECU was seeing voltage occasionally above 20V.

The problem that had prevented the car from running was intermittent O2 readings and p1166 and p0134 codes. The appearance of codes did not correlate directly to whether the ECU saw AFR. Since the V regulator was replaced, the factory wideband has not read at all.

The car’s wiring was unmodified since last year when it ran correctly. The car is a race car and the ECU and fuse boxes are only connected to tail lights and Engine-related sensors and components. The radiator fan and fuel pump are on parallel circuits and not connected to any of the car’s original wiring.

When the engine last ran, the main relay had been removed from the wiring and E7 left empty. The main relay has since been reinstalled. No codes are present. The Kpro board was changed over to a PND ECU (with the correct resistors and wires swapped or added as verified by Hondata) in an attempt to resolve AFR signal, suspecting damage from overvoltage. The main relay was installed just after installing the PND board.

Since the engine ran correctly, a non-zero value has been present for MAP after engine shutoff which goes back to zero after cycling power. It is a NTK wideband which was replaced last year after the old sensor was accidentally wired in reverse with the TPS.

ECU, engine, transmission, and chassis grounds have been thoroughly inspected or replaced. G101 is located on an m8 boss on the side of the K20Z1 cylinder head. Transmission ground is from an m6 case bolt to the chassis rail. Engine ground is from a RH engine mount bracket m10 to chassis. The battery is located where the RH seat would be, and is grounded to the floor. Two of the ECU ground wires to G101 had some corrosion in the last few inches before the ground. Those wires were replaced.

After being unable to resolve the AFR signal, a PLX wideband was installed. After seeing no AFR reading, I found that I had used an incorrect, home-made wiring diagram, and had wired pin 3 in the 4-pin PLX connector to Kpro analog ground. Pin 3 was outputting 8V. AN0 is now the only input being used on the KPRO board. Kpro was then able to see AFR and trim the AFR values. 12v wideband controller power comes from fuse 4, and grounds to the wirewall.

When the car was first started after the engine rebuild, idle was normal. Now, there is a surge from about 550-800rpm at about 0.5hz.

The datalog shows erratic fluctuations in INJ, IGN, AFR, battery V, and under some conditions, TPS. Of course, it runs horribly and is undriveable.

I have missed many events because of these ongoing problems, and hope that my entire season will not be lost. Thanks very much for the help.

[Spunkster]

When you tested this ECU on a known working vehicle, did you upload the calibration for their vehicle?

[bemmis]

Yes, the calibration was changed to match the stock 03 Civic Si it was tested on. Immobilizer was turned off. I also tried the low octane tune. It was crank, no start for both, with no fuel pump priming.

It's probably irrelevant, but after receiving the Kpro in 2017 when the car was close to stock, it was never able to run with the immobilized enabled. That was the original ECU from the car - kpro has now been moved to a known good PND while troubleshooting these issues. I never troubleshot the immobilizer and have always used it with the immobilizer turned off.

Thanks

[Spunkster]

What is the serial number that is on the K-Pro board inside the ECU?

[bemmis]

The serial number on the board is 43412

[Spunkster]

Send an email to support <at> hondata.com with the following and I will issue an RMA and give you further
instructions:

Name:
Address:
Phone:
Email:
Serial#:
Description of problem:

Include a link to this thread

[bemmis]

Thank you.

One more detail is that S02 is at 4.08V desire noting being wired to the ECU input. This began after the factory wideband stopped being seen in Kpro.

[bemmis]

One more detail is that SO2 is at 4.08V despite nothing being wired to the SO2 ECU input. This began after the factory wideband stopped being seen in Kpro. Sorry for the typo.