Can't get romeditor to read the correct voltage for lambda

[racerxadam]

The set up:
88 CRX si
1st gen b16
obd-1 p28
obd-1 conversion harness by blown90hatch
hondata 4b
FJO wideband

Now for the problem. No matter what I do I can't get hondata to read the correct values from the fjo. The voltage from the fjo is correct using a multi meter but when i hook up the wires to the stock o2 sensor wires and connect rom editor the voltage is way off. I tried putting a diode in the ground wire like hondata says on the website regarding cars that have an earthing problem, but the radio shacks near me only had 200v 1A diodes. The reccomended diode is 50V 1A. Is the diode that different? Anyway, the diode made no difference in the voltage readings whatsoever. I also had the same problem when my car was obd-0.

I'm hooking the wires from the FJO up to the o2 sensor wires right at the ecu. They come off the conversion harness and are there to hook up to a 4 wire o2. I loaded a map in open loop so the ecu isn't looking for an o2 sensor.

I also soldered a 1K ohm resistor across the wires for the o2 heater circuit but I'm still getting a code for the o2 heater.

The only thing i can think is that there is something not compatible with the conversion harness, which I find very hard to convince myself of considering the number of people using blown90hatch's harnesses with no problems. The one thing that confused me about the harness is that the four wires that come out of it to be attatched to the 4 wire o2 all stem from another wire that goes directly from plug to plug on the harness.

Any experienced tuners run into this? Anybody at all run into this?

BTW blown90hatch is from honda-tech.com

[Peter]

sometimes u have to create your own values in rom editor to match with the FJO its explained in hondata website.

[racerxadam]

I know how to change the values. rom editor uses a voltage that is ouput by the FJO to calculate a/f ratio based on the values that you enter in the conversion chart. The problem is that rom editor is reading a different voltage than what is actaully there. I have verified that the voltage output from the FJO is in the correct range for the values I am seeing on my wideband readout. When you connect rom editor to the ecu you can also see the o2 voltage next to the a/f display like this



Thanks for your reply.

[Hondata]

Wire the lambda output directly into the ECU, making sure you use the correct pins (D22 & D14). Make sure the vehicle wiring or adapter harness doesn't ground SG2 (D22). Put a multimeter between D22 and D14; compare the reading to HondaLogger. If the voltage agrees then trace back towards the lambda meter to find the fault in the wiring.

This is often overlooked: There are four different grounds in the car, and all are different (power ground, logic ground, signal ground, shield ground). There's also two signal grounds. Each ground must go to the correct sensor/ground point as per a stock vehicle, otherwise the sensors will not read correctly. Shields are normally grounded only on one end.

[racerxadam]

thank you for the informative reply

[racerxadam]

I don't understand why it would effect the readings if D22 touches chassis ground. Inside of the ecu D22 has a direct connection to B2 and B2 has a direct connection to chassis ground on the factory wiring harness for the civic that the p28 came in. By that logic D22 will have continuity to chassis ground on a factory car with no modifications.

[true]

Wire the lambda output directly into the ECU, making sure you use the correct pins (D22 & D14). Make sure the vehicle wiring or adapter harness doesn't ground SG2 (D22).

I'm having the same problem as racerx and I have basically the same setup. All of my wires go directly to the ECU, EXCEPT D22 (signal ground) which is 'tapped' on. As racerx states I don't see how this can be a problem since the factory obd1 cars D22 hits chasis ground. Are you saying factory obd1 cars are having to un-groun D22 for this to work?

I'm going to check my voltage coming out of my wideband and make sure it agrees with what my LCD says the A/F is tonight...

[racerxadam]

I went and verified that D22 is grounded by finding a car that has untouched wiring and came with a p28. With all three ecu plugs plugged in D22 is grounded to chassis ground. With only plug D plugged in D22 does not ground to chassis ground. How can i get the o2 ground signal to be the only thing on D22 with out hurting the performance of the other sensors that are wired to D22 somewhere else in the harness?

While I was fooling around with the wiring I decided that I wanted to see what would happen if i grounded D22 to chassis ground right at the ecu and it brought the voltage within .2 volts of the actual measured voltage. That is much closer than the entire volt that it was off by before. With the key in the off position I get a steady 0 ohm resistance from D22 to ground but once the car is started I get around 30 ohm. Is that normal? It seemed that when i grounded D22 reducing the resistance considerably that the values came much closer to what is expected.

[Hondata]

With a stock 95 Civic if I test the voltage at the ECU with a voltmeter and compare it to HondaLogger they are almost exactly the same (about 0.01 V difference).

All the grounds from the ECU should merge into one connection to the vehicle chassis (G101), but it is still very important to use D22 as the ground for the lambda meter rather than anything else, especially the heater ground or shield ground.

You still need to wire the lambda directly into D14 & D22, compare voltages between HondaLogger and the mutimeter, and start tracing towards the lambda meter. Once all the voltages match up, then start worrying about lambda.

If you really have too you can adjust the HondaLogger/RomEditor voltage to lambda settings to take account of the ground offset in the wiring. Add the same voltage value to all values in the 'o2 sensor voltage' column until the lambda and HondaLogger o2 voltage agree.

[racerxadam]

I have my wideband output wired directly to the ecu at the ecu to pins D22 and D14. With the wideband unattached from the ecu I get a voltage reading of approx. 2.5 volts at idle. According to the FJO a/f v. voltage output graph that is around 14.7 a/f ratio. My LED display also reads approx. 14.7. As soon as I attach the leads from the wideband to the wires from the ecu and test the voltage with a multi meter the voltage jumps to 3.5 volts.This is what concerns me the most. Why does the voltage output measured with a multimeter change when the leads are wired to the ecu? Hondalogger is also reading 3.5 volts but at 3.5 volts the a/f ratio according to the chart for the FJO is over 19:1.

At this point the multimeter and hondalogger are reading the same voltage and i could add voltage to the conversion table to compensate but the curve for the voltage output from the wideband is not linear and there for the voltage to be added at different points will vary

[Hondata]

The FJO output voltage should not change when you connect it to the ECU. I just checked mine and it only changes by about 0.01V when you disconnect and reconnect it.

Double check the analog output wires from the FJO power connector. Analog output should be pin A, analog ground pin B. A and B are stamped on the vehicle side of the connector (C & D are on the FJO side).