I have a 91 CRX DX with a JDM D15B with a CRX SI D16A6 distributor. I decided to stay OBD-0. I did the multiport wiring myself and it ran fine for a week, until i got a check engine light with code 4. I used the troubleshoot tree on the repair manual and everything was fine except for the last step where it asked to check for continuity between the orange wire on the ECU plug and any ground. If there is no continuity, then it says to replace the ECU, if there is continuity it says that there is an open in the orange wire. I took the pin with the wire off the ECU plug and place another wire and connected it straight to the distributor plug. I did all the tests again and got to the same place. I still have continuity but I know for a fact that I dont have an open wire. Any help would be appreciated. Thanks

 

don't know what manual you are using but it doesn't sound the same as the Factory Service Manual which says:
turn ignition switch off
remove hazard fuse from main fuse box for 10 seconds to reset ECU
start engine
is check engine light on? does LED indicate code 4?
if yes,
stop engine
disconnect the round 8 pin connector from the distributor
measure resistance between C and D terminals on the connector on the distributor(the 2 right in the center of the connector)
is there 350-550 ohms?
if no, replace distributor
if yes,
check for continuity on the distributor connector (wiring harness still disconnected) between the C and D terminals (individually) and body ground
does continuity exist?
if yes, replace the distributor
if no, reconnect the connector and go to the ECU and measure resistance between ECU pins B10 and B12 <U>(not between pin and ground as you were checking)</U>
is there 350-550 ohms?
if no, repair open in orange and/or white wires
if yes, substitute a known good ECU and recheck
if code goes away replace the ECU

 

When I wrote the first part up at the top, i was just writting it from memory, but here i have the info and it says

1.Remove Hazard fuse for 10 sec
2.Start engine and verify CHECK ENGINE light
3.If LED is flashing Code 4 go to next step, if not, problem is intermittent
4.Unplug 8-wire TDC/CRANK/CYL plug connected to distributor
5.Check resistance between "C" and "D", it should be between 350 and 550 ohms
6.If its NOT within specs, replace distributor
7.If its within specs, check continuity between ground and terminals "C" and "D"
8.If continuity exists, sensor is shorted to ground, replace distributor
9.If continuity didnt exist, reconnect 8-wire plug and connect ECU test harness
10.Measure resistance between b10 and b12, if resistance is not 350-550 ohms,
repair Orange and/or White wires.
11.If resistance is within specs, check continuity between b10 and ground
12.If continuity exists, repair short in Orange wire between ECU terminal b10 and
distributor connector.
13.If continuity didnt exist, substitute a known good ECU.

YOUR FORGOT steps 12 and 13. In the steps you check for continuity twice. Once at the begining on the distributor and then again at the ECU. Since I have continuity at the ECU, it says i have a short somewhere in that wire, but i rewired it straight to the distributor plug and I still have continuity. I also checked the other two sensors in the distributor (Top dead center sensor and cylinder sensor) and I also have continuity in those 2 so I have a short in all 3 sensors. Any help would be appreciated.