reading codes and trouble shooting

[stevemd24]

I have an Rb20det in a 1972 240z

It went in limp mode in the middle of a drive to Safeway :*( I am not an expert on reading flashing lights can anyone help me out, tell me what the lights on my ecu are saying.


As far as i know limp mode normally means you have a problem with your water temp senser or maf, and both mine seem to check out just fine,
i swapped out the maf, senser and even the ecu with stock equipment and it didnt change anything, it still stalls at 3500 rmps or so

Idles fine, burns extra gas can smell it out the back end, but its undriveable

thanks for your help hope the video works

[Yellow4g63]

Diagnostic for the rb20det ECU

The ECU is in the passenger footwell, behind the plastic kickplate to the left of your feet. You'll have to remove the computer from the mounts in the footwell, as the led/leds you'll need to see are pointing towards the front of the car. Switch on the ignition but don't start engine, the led on the ECU will begin glowing turn the selector screw clockwise all the way.

There's three types of factory ecu in Skylines, One type has two LEDs and five modes, the other type has one LED and two modes and the last type has no LEDs, the output is done with the engine check light in the instrument cluster.

For two led ecus the led will flash once, pause, flash twice, pause... all the way up to five this is the diagnostic mode Mode 1 = one flash, mode 5 = five flashes. When you reach the right mode, turn the screw back counter-clockwise. Mode 3 is what most people use.

For one led ecus wait a couple of seconds, and turn the screw back counter-clockwise, the ECU is now in mode 2 the engine check light on the dash will mirror the LED on the computer.

The led will flash out a code or series of codes if there is more than one fault More recent ECU's have two LED's red is first digit, green is second digit, eg red 2x flash, green 1x flash = code 21. The ecus on most R32's have one LED, long flash = first digit, short flash = second digit, eg long, long, short = code 21.

Codes:
11 Crankshaft position sensor
12 MAF sensor circuit
13 Coolent temperature circuit
14 Vehicle speed sensor circuit
21 Ignition circuit
31 ECU
34 Knock sensor
43 Throttle position circuit
45 Injector leak
51 Ignition circuit
54 Auto signal to ECU
55 All OK
Turn the ignition off to put the ECU back to normal.

There is also a O2 sensor test in real time available - do the above to get the ECU into mode 2 (single LED ECU) or mode 1 (2 LED ECU's) Start the engine. Warm the engine, and then run under no load at 2000 rpm for the test. Single LEDs: on = lean, off = rich Dual LED's: green LED on = lean, green LED off = rich

From someone on the interwebz named niall. Took a few seconds with google to find the answer.

[stevemd24]

no offence but i can copy and paste as well

the ecu isnt in my footwell as its in a 240z swap

I already read all that crap, i am asking someone to help with my answer not some generic cut and paste as i said i am not an expert on reading these lights, and i posted a video to ask someone to read the lights for me, and maybe give me real advice on my limp mode options

just in case u missed it in the first post

[Yellow4g63]

Didn't watch your video because you were asking how to read the lights. The stuff I copy and pasted tells you how to read them. I just watched the video and it's throwing 3 codes. Tell me which codes you got from reading it and I'll tell you what I saw.

[Yellow4g63]

Not been a d!ck about it just trying to teach you how to read the code. slow flashes are the 1st number fast flashes are the 2nd number to the code.

[stevemd24]

well it looks like

54 Auto signal to ECU
and maybe
13 Coolent temperature circuit

[lexcrob]

The video shows 12, 13, 54.

First thing would be to disconnect battery and put pos and neg terminals together for 10 sec. (with them disconnected*)

(this discharges any capacitors in the ecm and wipes its codes/memory)

Then run the car again for a bit up and down the block or at least idle for 15min.

Then see what comes back.



If code 12 returns that will be the easiest to trouble shoot as its a 2 wire sensor. One wire goes right back to the ecm for its signal. The other goes to a ground which "dasy chained" shared by tps and maf and other things. Your problem could be just a poor ground id suggest just adding a bunch. It could also just deal with a fault in that it took the engine too long to heat up hence you get that code. Such as the thermostat is stuck open low on coolant.

The code 54 is no auto signal which means your ecm is not communicating with the tcm (trans control module) I assume you have an auto ecu there may be a way to ground or pwr it to bypass ....

Anyways good luck!

[Yellow4g63]

well it looks like

54 Auto signal to ECU
and maybe
13 Coolent temperature circuit

Yeah you got it. the 1st one to flash was 12, then it paused for a second or 2 then did one slow flash and 3 quick flashes. You got 2 out of 3 pretty much mastered it

Check the maf wires and coolant temp sensor wires. Sometimes the coolant temp will go bad tho. The auto ecu signal code prob needs a ground on one of the wires but I don't think it will throw a check engine light after the other 2 are gone. If you get Nistune or a tuned chip the light will go away because they will flash a MT bin on it.

[stevemd24]

i am sure the auto code is do to me runnin an auto ecu in an manual but i will reset the box and redo it

thanks for your help i will keep u guys updated

[stevemd24]

i have another ecu with nistune in it, but i put in the stock one to check to see if my problem was the ecu itself,

I put in a wiring harness from wiringspecialties.com i bought a used maf stock from ebay,

so far nothing has worked

[Yellow4g63]

Do you have the software too? or just the ecu? double check the harness maybe it's getting grounded out some place.

[stevemd24]

i downloaded the software but not completly sure how to use it yet

[Yellow4g63]

You need a consult cable to connect to the consult port. You can get one from a 91 and up sentra. After you get you need to load the address file for the R32. The user manual on the web page is very helpful check it out.

[stevemd24]

ok i got the cable, its asking me what car i have,

since its just an engine how do i know what to pick

its an rb20det, but i am not completly sure of the year, its got a black top

[Yellow4g63]

HCR32 Skyline address file will work.

[stevemd24]

ok i installed nistune,

now help figure out my maf problem what should i look for,

what would u guys need to see to help me figure out the problem?

[Yellow4g63]

I would check the voltage at the maf plug with a volt meter. check the ground too with a continuity test. If it acts the same when it's unplugged might be the harness cutting chaffed along the way. If the harness is good and voltage is good then it's the maf taking a dump.

[stevemd24]

there is power going to the ecu from the malf pin number 17

[Yellow4g63]

check at the maf plug.
http://public.dm1.livefilestore.com/y2p ... s=45514299

12v power and 5v signal if I remember right.

[stevemd24]

Not sure if this helps any got this off nistune, i am going to have to look up the wiring to test the maf directly



i have both

Z32 VG30 (80mm)
Wire A - Not Connected (orange)
Wire B - Signal (shielded white)
Wire C - 12v Ground (black)
Wire D - Signal Ground (shielded black)
Wire E - 12v Power (white)
Wire F - Not Connected


and

R32 RB20 (80mm)

Wire A - Not Connected
Wire B - Signal
Wire C - 12v Ground
Wire D - Signal Ground
Wire E - 12v Power

and they both have the same problem,

[USMCgetsome]

take clearer pics. it's really blurry man. The basic thing to look for on the maf is voltage. see if it's constant or as you depress the throttle that it increases with rpm.

[stevemd24]

yea sorry the sun is to bright for my computer at the moment,

[stevemd24]

thanks for the help guys, the car runs great now,

now to fix other problems,

cooling fan isn't hooked up
tachometer isn't hooked up
fuel gauge isn't hooked up
break lights are not hooked up,
stereo isn't hooked up

[Yellow4g63]

Run the fan clutch it will keep the car cooler than electric fans.