Looking at the OBD1 pin out the relevant pins are B11-B16 I believe. However, can someone explain what pin does what? I'm guessing B11 and B12 are the cam sensor but what is P and what is M? TDC is probably a blip that occurs right when cylinder 1 is at TDC? That leaves B15 and B16 as the crank signal.

B11-CYP P CYP(#1 piston position) -P Orange, CYP sensor input, n/a
B12-CYP M CYP -M White, CYP sensor signal, n/a
B13-TDC P TDC(top dead ceter) -P Org/Blue, TDC sensor input, n/a
B14-TDC M TDC -M Wht/Blue, TDC sensor signal, n/a
B15-CKP P CKP(crank position) -P Blu/Green, CKP Sensor input, n/a
B16-CKP M CKP -M Blu/yel, CKP Sensor signal, n/a

Does anyone know the nature of these signals? i.e. 30-2 teeth wheel/falling edge, etc?

 

They are all variable reluctance or VR sensors.

Here is a little bit of info;
Distributor Pick-ups, VR-Sensors

 

Yeah I know that. I wanted to see if anyone knew how the signals transmitted over those pins I listed above.

 

Looks at the wheels...

24 teeth
1 tooth
4 teeth

Its a 24+1 trigger and I'm not sure of the actual cylinder position sensor (4 teeth) or what it does for stock code

 

The signal is transmitted as a pulse of alternating current. It requires an oscilloscope to measure it.

The P = Detects the signal (frequency) sent out as related too the teeth on the cranks/cams speed. The M = the drop between/change between pulses. At least that's how I read it.

The manual says that P = signal and M = Ground.

The CYP in most OBD1 & 2 Honda's is a one tooth VR sensor located in the distributor. Where it is located on the cam there would be 4 pulses per complete 720° crank rotation. It detects the position of the No.1 cylinder to determine the sequential fuel injection for each cylinder.

 

ECU doesnt need all three sensors to do Sequential Injection though...all it needs is a crank (24 teeth) and a cam pulse (could be 1 pulse per cycle or could be 4). Im honestly not sure which the ECU uses and/or why the other is there as well. Has to be a reason, just never needed/bothered to find out.

Im guessing TDC sensor is the 1 tooth pulse and the CYL is the 4 teeth (to represent each individual cylinders TDC). Im also guessing the reason for both is in the case one sensor fails, the ECU can still do a relatively good job of keeping the motor running nicely.

 

I may try and do some datalogging with my Arduino Uno to see what exactly the signal train looks like on all three pins. My only question is how can I splice into these signals and read them without affecting them? I don't want to pass them through the Arduino for now since I'm not sure that it can react fast enough.

 

Here are the definitions for each sensor straight from the Honda PGM-FI manual.

• The CKP Sensor determines timing for fuel injection and ignition of each cylinder and also detects engine speed.

• The TDC Sensor determines ignition timing at start-up (cranking) and when crank angle is abnormal.

• The CYP Sensor detects the position of No. 1 cylinder for sequential fuel injection to each cylinder.

So like you said, only two sensors are really used, the CKP and CYP.

 

I'm not sure if you guys have seen this before, but we've used this to convert 4AG Toyota distributor signals to digital square-wave for standalone EMS conversions.

http://jbperf.com/dual_VR/v2_0#Buy

You could easily use this on the Honda CYP/CKP sensors.

 

It is a 24 and 1 cam and crank setup. However the other sensor with 4 is usually used for quick startup. So the stock computer does not have to wait the entire revolution to start the vehicle on the 1 TDC.

 

Is there anywhere I can find a copy of the Honda PGM-FI manual?

 

It all depends on what you are looking for in the manual. If you are looking for exactly how the FI system works than there really isnt a manual for that. If you are looking for some description and wiring diagrams and test procedures you can pick up a factory service manual for the vehicle. Usually you can buy them at any Honda dealer. Alldata also has a lot of the information on their site as well, but it is a pay service.

 

GhostAccord said "Here are the definitions for each sensor straight from the Honda PGM-FI manual."

I was simply asking what this "Honda PGM-FI manual" is.

 

He was most likely referring to the factory service manual. Not the Helms ones, but the actual Honda Factory Service Manual.

 

Do a search on the text posted by Ghost Accord.....

 

TDC is 5 events per CYL waveform.

 

Example:

http://ww2.justanswer.com/uploads/th...9_dtc_1362.pdf

 

u sir deserve a metal! CAN SOMEONE STICKY THIS, OR AT LEAST ARCHIVE?! i've spent the last 5 hours searching for this! let alone the month i've been trying to figure out why my car runs with the TDCM AND CKPM switched around.. (sorry to bring up an old post).. JUST NEEDED TO EXPRESS MYSELF!