Reset ECU Codes.

[HotRodGuy]

My speedo on my '91 was going crazy and the cruise won't work anymore so I took it to my friends shop and we hooked it up to his computer diagnostic equipment. It said that I had a bad vehicle speed sensor, so I put a new one in it and the speedo still does the same thang. What up wit dat? Do you have to reset the codes in the ECU er sumpthin? Oh, the cruise still don't work either.

[Ni240sxt]

Disconnect Battery, leave it overnight to let the ECu reset itself? <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/sly.gif" border="0" valign="absmiddle" alt=':sly:'>

[HotRodGuy]

Ah-ha! I have to leave it over night, huh? I did disconnect it fer about two minutes and obviously that didn't work. I know that's all ya have ta do on GM vehicles. Thanks, I'll try it.

[geeaj]

Disconnect power to battery does NOT work. You need to clear the ECU by following the FSM procedure. If you don't a chiltons or FSM, goto www.240sx.org for a detailed procedure.

It is really easy.

[geeaj]

Here is the procedure for the sohc found on the 89-90 s13

How to Read Malfunction Codes for Your SOHC 240SX
=================================================
On most car, only a jump wire or a screw driver is required to read the trouble code store on the engine computer. This the case for the 240 sx. The following intructions allow you to easily read and erase trouble code on your car electronic control unit (ECU)

The instructions come from the nissan 240sx 1989 12 valves engine service manual. There is a good chance that later models are similar.

In a few word, reading to code require accessing to the ECU, placing the unit in self diagnosis mode using a screw driver and looking at the flashing lamps on the unit to see what code is displayed.

1. Accessing to the ECU

The ECU is located to the right of the passenger footwell. You need to remove two fastener of the right doorstep in order to remove the kick panel. To remove the plastic fasteners, unscrew the center part and pull out the other part. Two metal screw and a fastener hold the kick panel. Some kind of pitch is also present.

Under the panel you now see the ECU with its connector. Unfortunaly, you have to access to the other side of the ECU. Unscrew the unit and turn it 180 degree on the vertical axis without unpluggin it.

You now see the front of the unit. An ajustment screw, a green inspection lamp and a red one are present. The screw is use to adjust the idle speed and to change the diagnostic mode.

MARK THE ORIGINAL POSITION OF THIS SCREW. UPON DIAGNOSTIC COMPLETION, RETURN THE SCREW TO THE PREVIOUS POSITION. OTHERWISE, ENGINE IDLE SPEED MAY CHANGE.

2. The ECU modes

The electronic control unit have five mode:

Mode I- Exhaust gas sensor monitor (Normal mode)
Mode II- Mixture ratio feedback control monitor
Mode III- Self-diagnostic
Mode IV- Switch on/off diagnostic system
Mode V- Real-time diagnostics system.

The unit automatically return to normal mode I when the ignition is switched off.

Only mode III will be studied here. Troubles code are stored on mode III. The stored codes will be lost if the car battery is disconnected or if after selecting mode III, mode IV is selected.

3. Changing to mode III.

- Turn the ignition 'ON'
- Turn the ECU adjusting screw fully clockwise.

The inspection lamps will flash onces, the unit will be in mode I. The inspection lamps will flash twice, the unit will be in mode II. The inspection lamps will flash 3 times, the unit will be in mode III. The unit will continually cycle through the five modes until the screw is turn back.

- Turn the screw back after the lamp has flashed 3 times.
- You are now in self diagnostic mode III.

4. Reading the trouble codes.

The codes are indicated by the number of both red and green lamps. First the red lamp flashes and then the green one. The red lamp correspond to units of ten and the green lamp to units of one. For example, when the red lamp flashes once and the green lamp flashs twice, this signifies the number "12".

The codes are:
11 Crank angle sensor circuit
12 Air flow meter circuit
13 Engine temperature sensor circuit
14 Vehicle speed sensor circuit
21 Ignition signal missing in primary coil
31 E.C.U. (E.C.C.S. control unit)
32* EGR function
33 Exhaust gas O2 sensor circuit
35* Exhaust gas temperature circuit
43 Throttle position sensor circuit
45* Injector leak
55 No malfunction

*California models only.

After the diagnostic, Turn the ignition 'off' to return to mode I.

To erase the memory, use mode IV. The codes are automatically erased from memory when the starter is operated fifty times after the trouble is last noticed.

[geeaj]

Here is the procedure for s13 ka24de 91-93

Only a screw driver is required to read the trouble codes stored in the ECU (Electronic Control Unit). The following instructions allow you to easily read and erase the Malfunction Code on your beloved's ECU.

These instructions come from the 1991- 16 Valve Factory Service Manual.

Reading the codes requires accessing the ECU and placing the unit in one of two self diagnostic modes using a small flat head screw driver. The codes are displayed by a single RED L.E.D. in the ECU and the Check Engine Light.

1. Accessing to the ECU

The ECU is located at the right of the right side footwell. The "side" is determined as you sit in the car facing forward. (For cars in North America, the right side would be the passenger side)

You need to remove 2- "rivet" type fasteners of the right doorstep in order to get the kick panel out. To remove the plastic fasteners, unscrew the center part and pull out the other part. 2- metal screws and another "rivet" type fastener hold the kick panel.

Under the panel, is the ECU with its connector. Unfortunately, you have to access to the side of the ECU that is against the firewall. Remove the two screws at the top and bottom of the ECU and gently turn it to get to the Model Selector and RED L.E.D. Don't unplug the ECU to do this!

BE CAREFUL!

There should be a small sticker by the Mode Selector that tells you to turn it clockwise to set the Modes and to be sure to return it all the way counter-clockwise to the original position when the car is in use. You will also see the RED L.E.D. inside the ECU.

IF YOUR STICKER IS GONE:

Mark the original position of the Mode Selector. This is a VERY IMPORTANT position for the Mode Selector! (This should be fully counter-clockwise).

2. The Diagnostic Modes

--------------------------

There are 2- Modes and 2- Conditions for the Engine to be in for running diagnostics:

All Modes are with the Ignition Switch in the ON position
Mode I (Engine OFF)- Bulb Check
Mode I (Engine ON) - Malfunction Warning
Mode II (Engine OFF)- Stored Self Diagnostic Results
Mode II (Engine ON)- Exhaust Gas Sensor Monitor

Note: The ECU will automatically return to Mode I when the ignition is switched OFF. When the ECU is changed from Mode II back to Mode I by using the Mode Selector, the malfunction code(s) stored for Mode II will be erased. More on this later.

3. Changing Modes

Note: Switching Modes is not possible when the engine is running.

* Turn the Ignition Switch ON.
* The ECU is now in Mode I.
* To switch to Mode II:

Turn the ECU Mode Selector fully CLOCKWISE, hold for at least 2-seconds and then return the Mode Selector to it's original position. You are now in Mode II.

* Return to Mode I by turning the Mode Selector fully CLOCKWISE again, holding for another 2-seconds and turning it back to the original position.

Note: Doing this will ERASE any Malfunction Codes that are stored in the ECU for Mode II.

Example: If you found a Malfunction Code of 34 when you very first switched to Mode II and then cycled back to Mode I, then again to Mode II, you'll get a 55 (everything's OK) code. This is assuming that you didn't start the car between changing modes. When you start the engine, any current malfunction codes will be store by the ECU until you erase them or they get dumped.

Malfunction Codes are stored by the ECU for 50 times of cranking the starter. Then they are erased. If the same conditions are present, the Malfunction Code will be stored again for 50 cranks of the starter. And so on...

4. Reading the Malfunction Codes:

The Malfunction Codes are indicated by the number of flashes by the RED L.E.D. and the Check Engine Light. You can read either one. They flash the same information. For example, when the RED L.E.D. flashes once and after a short pause flashes twice, this signifies the number "12".

Note: If you find that your looking at a RED L.E.D. and a GREEN L.E.D., you've got a different ECU than is described here. See the FAQ on this same page that was written by Richard Lestage for the SOHC ECU!

_

ALL TESTS ARE PERFORMED W/ THE IGNITION SWITCH "ON"

Mode I (Engine OFF)- Bulb Check:

In this Mode, the RED L.E.D. in the ECU and the Check Engine Light stay ON. If either remain OFF, check the bulb.

Mode I (Engine ON) - Malfunction Warning:
RED L.E.D. is OFF = OK
RED L.E.D. flashes =

For California Models Only:

Code # Description

12 Air flow meter circuit
13 Engine temperature sensor circuit
14 Vehicle speed sensor circuit
31 E.C.U. (E.C.C.S. control unit)
32 EGR function
33 Exhaust gas O2 sensor circuit
35 Exhaust gas temperature circuit
43 Throttle position sensor circuit
45 Injector leak

For Non-California Models:

RED L.E.D. ON = The ECU's CPU or the Crank Angle sensor is malfunctioning.

____

Mode II (Engine OFF)- Stored Self Diagnostic Results

Code # Description

11 + Crank angle sensor circuit
12 E Air flow meter circuit
13 E Engine temperature sensor circuit
14 E Vehicle speed sensor circuit
21 + Ignition signal circuit
31 E E.C.U. (E.C.C.S. control unit)
32 * E EGR function
33 E Exhaust gas O2 sensor circuit
34 Detonation sensor circuit
35 * E Exhaust gas temperature circuit
43 E Throttle position sensor circuit
45 * E Injector leak
54 Signal circuit from A/T control unit to ECU (A/T only)
55 No malfunction in the above circuits

* = California models only
E = Check Engine light will show this code.
+ = Check items causing a malfunction of the crank angle sensor 1st, if both #11 and #21 are displayed at the same time.

Mode II (Engine ON)- Exhaust Gas Sensor Monitor

* Warm up the engine and see that the Temperature Gauge is in it's usual position.

* Run the engine at about 2,000 RPM for about 2- minutes under no-load conditions.

* Make sure the RED L.E.D. or the Check Engine Light goes ON and OFF more than 5- times every 10- seconds; measured at 2,000 RPM under no-load. (This is easiest to do while sitting in the driver's seat and watching the Check Engine Light.)

After the diagnostic, Turn the ignition 'off' to return to mode I.

************************************************** ********

[HotRodGuy]

Wow! Thanks geeaj! I'll do that tomorrow night and let ya know how it turns out.

Mines a s13 ka24de '91 btw.

[HotRodGuy]

Woo-Hoo! I got it fixed! <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/thumbs-up.gif" border="0" valign="absmiddle" alt=':thumbsup:'> Thanks geeaj, those instructions were right on target. My ECU still had code 14 in it which is Vehicle speed sensor. I reset it and everythang works again, only took about 30 min, easy as pie! &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=''>

[HotRodGuy]

Ok, I spoke too soon. This morning on the way to work everythang was fine until I tried to use the Cruise, it wouldn't work and then the speedo quit again. What gives? Is sumpthin wrong with my cruise and causing my speedo to quit or what? I'm wonderin' if I may have a bad connection or sumpthin. I'll check all my wires and connectors tonight. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/crazy.gif" border="0" valign="absmiddle" alt=':crazy:'>

[geeaj]

Hmmm...I believe that the code 14 for your Vehicle Speed Sensor may cause the faulty speedometer behavior that you described. I am not sure about the cruise control issue though.

These things don't usually go bad often, so if yours IS bad, you could do well to just swap a used one on. They are located pretty low on the tranny end. To remove if you'll need an open end 10mm wrench.. be careful not to strip that bolt, it's a PITA to remove if you do. Also, its plug resides near the front of the tranny, where the bellhousing mates with the engine block.

If someone out there has a FSM, please chime in. There is a procedure for testing the sensor with a voltmeter. I am not sure what the readings should reflect. 0.5 volts or something. I don't recall what the process is off the top of my head.

Let me know how it goes hotrodguy.

[geeaj]

Hotrodguy. Sorry I misread your post, you've already REPLACED the sensor. I am thinking that it could be the wire that connects the sensor. Did you replace that? I would do a continuity test on the wire, it could have a break in it or something. I would also check the connector on your speedo gauge as well.

Later.

[HotRodGuy]

Well, the new sensor came with a whole new wire, complete with connector.

Yep, that wuz my next plan, to check the car's wire and the speedo connector. I think that I may have a break in it sumwhere or a loose connector.

I'll let ya know what I find out.

Thanks!

HotRodGuy Out...

[TwoFourO]

I was just wondering what it means to have a California Model 240sx. I searched all over the place and I was unable to locate any information on this. The reason I am asking is because I pulled a code 45 from my ECU. This states that there is a Fuel Injector Leak but also says this code is for California models only. As far as I know the car came from Colorado. Does this mean if it was manufactured in California? I'm lost somebody please help. I checked the injectors for leaks and could find none. There is no smell of gas coming from anywhere around the injectors either. Thanks, -Josh

[8kred]

old post but did you ever get that sensor fixed?

[Pignose_Jorge]

Old ass post but i have a 89 fastback or hatchback how i say and the check engine light blinks 1-5 as well, i havent done anything to the ecu yet but i will, just wanna know if any of you got that fixed yet

[kichigai1]

Originally Posted by geeaj

Here is the procedure for the sohc found on the 89-90 s13

How to Read Malfunction Codes for Your SOHC 240SX
=================================================
On most car, only a jump wire or a screw driver is required to read the trouble code store on the engine computer. This the case for the 240 sx. The following intructions allow you to easily read and erase trouble code on your car electronic control unit (ECU)

The instructions come from the nissan 240sx 1989 12 valves engine service manual. There is a good chance that later models are similar.

In a few word, reading to code require accessing to the ECU, placing the unit in self diagnosis mode using a screw driver and looking at the flashing lamps on the unit to see what code is displayed.

1. Accessing to the ECU

The ECU is located to the right of the passenger footwell. You need to remove two fastener of the right doorstep in order to remove the kick panel. To remove the plastic fasteners, unscrew the center part and pull out the other part. Two metal screw and a fastener hold the kick panel. Some kind of pitch is also present.

Under the panel you now see the ECU with its connector. Unfortunaly, you have to access to the other side of the ECU. Unscrew the unit and turn it 180 degree on the vertical axis without unpluggin it.

You now see the front of the unit. An ajustment screw, a green inspection lamp and a red one are present. The screw is use to adjust the idle speed and to change the diagnostic mode.

MARK THE ORIGINAL POSITION OF THIS SCREW. UPON DIAGNOSTIC COMPLETION, RETURN THE SCREW TO THE PREVIOUS POSITION. OTHERWISE, ENGINE IDLE SPEED MAY CHANGE.

2. The ECU modes

The electronic control unit have five mode:

Mode I- Exhaust gas sensor monitor (Normal mode)
Mode II- Mixture ratio feedback control monitor
Mode III- Self-diagnostic
Mode IV- Switch on/off diagnostic system
Mode V- Real-time diagnostics system.

The unit automatically return to normal mode I when the ignition is switched off.

Only mode III will be studied here. Troubles code are stored on mode III. The stored codes will be lost if the car battery is disconnected or if after selecting mode III, mode IV is selected.

3. Changing to mode III.

- Turn the ignition 'ON'
- Turn the ECU adjusting screw fully clockwise.

The inspection lamps will flash onces, the unit will be in mode I. The inspection lamps will flash twice, the unit will be in mode II. The inspection lamps will flash 3 times, the unit will be in mode III. The unit will continually cycle through the five modes until the screw is turn back.

- Turn the screw back after the lamp has flashed 3 times.
- You are now in self diagnostic mode III.

4. Reading the trouble codes.

The codes are indicated by the number of both red and green lamps. First the red lamp flashes and then the green one. The red lamp correspond to units of ten and the green lamp to units of one. For example, when the red lamp flashes once and the green lamp flashs twice, this signifies the number "12".

The codes are:
11 Crank angle sensor circuit
12 Air flow meter circuit
13 Engine temperature sensor circuit
14 Vehicle speed sensor circuit
21 Ignition signal missing in primary coil
31 E.C.U. (E.C.C.S. control unit)
32* EGR function
33 Exhaust gas O2 sensor circuit
35* Exhaust gas temperature circuit
43 Throttle position sensor circuit
45* Injector leak
55 No malfunction

*California models only.

After the diagnostic, Turn the ignition 'off' to return to mode I.

To erase the memory, use mode IV. The codes are automatically erased from memory when the starter is operated fifty times after the trouble is last noticed.

Nice write up!

There were a few confusing thing that I wanted to clarify in order to read the trouble code.

In Step 3. Changing to mode III.

- Turn the ignition in the ON position (Do not start the car)
- After the diagnostic, Turn the ignition to the OFF position (where you can take the key out) to return to mode I.

Unfortunately the instructions to erase the memory or trouble code did not work for me. After doing more research, I finally found this one which did the trick. Just thought I share it with everyone.

To Erase the Memory or Trouble Code:
After you read the code, you can start the engine
Turn the bolt back to the clockwise position for at least 2 seconds(While running)
Turn it back to the counterclockwise position
Now shut the car and then start it again, this should of removed the code."