Jump to content

Checking ECU Error Codes


87cquest
 Share

Recommended Posts

This question gets asked a lot by people, and I was hoping we could put it in the FAQ section.

 

The easiest and cheapest way to check for ECU error codes is to go to Radio Shack and buy a 12v LED for about $2.50.  

http://www.cgwebdesign.com/quest/led.jpg

 

Once you have your LED, it's best to solder aligator clips onto each wire.  I've heard you can go without them, but I've never got it to work without them.  

 

Once you have your LED ready to roll, it's time to test for codes.  I was surprised as to how easy it was to check for these.  

 

Open the glove box, and squeeze the sides to drop it all the way down.  Get down and look up and you will see a white/yellowish colored plug with nothing plugged into it.  Take the LED and hook the red lead up to the most upper right terminal, and the black lead to the most lower left terminal.  Once you have done this, you're just about done.  Just start the car, or turn the key to the "On" position.  

 

If there are any errors, the LED will blink a certain amount of times.  The amount of blinks determines the error.  For example, 1 blink then a pause, then one blink again, is code #1.  3 blinks, then a pause, then 3 blinks, again, and so on and so forth, is code #3.  Note - It will always give you a code 1 (o2 sensor) until the car warms up, and the car must be started to test this.

 

Here are the codes:

1 - o2 Sensor

2 - Ignition pulse

3 - MAS

4 - n/a

5 - TPS

6 - ISC

7 - Engine coolant temp sensor (two prongs, not one)

 

After you've checked the codes, and fixed whatever was wrong, unplug the battery for a minute to reset your ECU.  Hope this helps.

 

~Carlos

Link to comment
Share on other sites

  • 2 months later...
  • 3 weeks later...
are all years of this car checked this way?  i think i saw somehere that earlier models have the connectors in the engine bay....not sure but someone who knows breakdown for us which years have the connector behind the glove box and which years don't.
Link to comment
Share on other sites

  • 2 weeks later...

A really slick way to hardwire this would be to get an "illuminated" type of switch from radioshack or someplace.   Make sure to get a 12v one, if its 120 v the light may be too dim...

 

That type of switch has 3 connections:  a "12 volt in",  a "12 volt switched out", and a "to ground"

 

Simply wire one of the wires mentioned by 87cquest to the "12 volt in" and the other to the "to ground" and you've got a switch that gives you error codes :)

 

MikeMeyerhoff

Link to comment
Share on other sites

I went to check my codes today. My diag. connector only has 5 pins, is this right??? Anyway, I plugged in the LED and waited for about 10 minutes with the engine running. Nothing lit or blinked at any point. Is there something wrong OR is there nothing wrong at all? Doesn't the LED supposed to light at first when you turn the key to ON?? Thanks, my ISC has been acting up so I decided to check it.
Link to comment
Share on other sites

if it's the in dash connector, it should work as long as you are using a 12V DC LED,

not a high voltage AC unit.

 

I just had a chance to look, 5 pins it is.  You can also check cruise and ETACS with this connector.

Link to comment
Share on other sites

I did it again today, I reversed the wires the other time 'cause I was upside down, hehe. After the car was warmed up, the 12V LED kept blinking, with a 2 sec interval. Blink, pause , blink, pause. It looked like 1 blink, no other intervals. Does this mean it's the O2 code? I have a 3-wire sensor which is fairly new,and the car doesn't run rich at all, except when on boost and a little when idling (I'm using a Halmeter)
Link to comment
Share on other sites

Under normal conditions it should go steady ON when warmed up, and a single flash repeated means 02.  I can't say tho how a three wire might or might not affect the readings (?)

 

Have you pulled the neg battery cable after doing any work - like changing sensors?

 

You would need to in order to clear the memory of that code...

Link to comment
Share on other sites

Thanks alot, yeah, I always pull the neg. cable after resets or changing sensors. The LED had a solid light on at first, then blinked once. I don't know if the 3-wire acts different, either, but that's the least of my problems, the car doesn't run overly rich so I'm not too worried. As long as there isn't other codes that come up.
Link to comment
Share on other sites

  • 1 month later...
Anyone know where the diagnostic connector is on an 84?  I cannot find mine to save my life.  Ive dropped the glove box and its not there.  I couldnt find anything under the hood.   I also didnt see it in the drivers side footwell where my DSMs plug is located.  Anyone got any ideas???
Link to comment
Share on other sites

  • 2 months later...
  • 2 weeks later...

Hmmm - under the steering column?  I dropped my column to replace a bad ignition switch; didn't happen to notice a "stray" connector - then again, I wasn't looking for one...

 

However, I have looked for the diagnostics connector on my '84 - couldn't find it.  So, I pulled the kick panel cover off at the ECU and just stuck the VOM probes right in the connector.  It would be nice to have hard-wired indicator..

 

Mike

Link to comment
Share on other sites

For 85/86 model years, the ECU diagnostic connector is a round connector located near the air filter canister -- right next to the fuel pump test connector.

For 83 model year, there is no diagnostic connector.  I couldn't even find an ECU  diagnosis wire in the 83 wiring diagram.  

For 84 model year, you may have to tap at the ECU connector as posted earlier.

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

Page 14-23 of my 85 Conquest Manual gives instructions for using voltmeter and

Page 14-49 of Fuel (ECI) System section of my 88 Conquest Manual

 

1) Turn ignition switch to OFF.

 

2A) - for 86 and older

...1. Position self-diagnosis 3 pin connector such that,

the single pin is at the top and the dual pins are at the bottom. Connector is

located in engine compartment near Air Can and Fuel Pump diagnosis 2 pin connector.

...2. Connect voltmeter positive to upper single pin (signal, light blue+yellow wire). Connect negative to lower right pin (ground, black wire). FYI - lower left pin (white wire) is O2 sensor diagnosis connector.

 

2B) - for 87 and newer

...1. Locate the self-diagnosis 12 pin connector behind glove box.

...2. Connect voltmeter positive to upper right corner pin (signal, black+red wire).

Connect negative to lower left corner pin (ground, black wire).

 

3) Turn ignition switch to ON. The contents of memory will immediately start. Under normal error-free conditions, the pointer of voltmeter constantly indicates 12V. Abnormal conditions, count the number of 12V pulses between 2 second 0V readings. For example -- Two 12V pulses + 2 sec 0V + 4 12V pulses + 2 sec 0V = error codes 2 and 4 = bad ignition and bad Pressure Sensor.

 

4) Turn ignition switch to OFF.

 

5) After replacing/repairing defective part, disconnect negative terminal of battery for 15 seconds to erase abnormal error code.

 

 

01 - O2 sensor

02 - Ignition Pulse (engine speed sensor)

03 - Air Flow sensor

04 - Boost Pressure sensor (only for 86 and older)

05 - Throttle Position sensor

06 - ISC motor position sensor

07 - Intake Coolant Temp sensor

Link to comment
Share on other sites

  • 4 months later...

Hooked up my 12v LED today. Didn't get the LED light to come on  :-/

 

Tested the LED direct to the battery, works fine.  Should the LED stay on even with no errors ???

Link to comment
Share on other sites

the first couple of tries for me didn't light either.  give it another go, with the car running and cold yu should get a signal for 02 sensor - single flash repeated.  when it warms up in a minute or two it should go steady ON.
Link to comment
Share on other sites

Here is a pic of one hooked up.  Notice the pin pattern, the two sides are different.  The easiest way I remember to hook it up is:

 

The red goes on the passenger's side of the car in the last row.  There is only one pin on that row, use it.

 

The black goes diagonal from it on the driver's side of the connector.

 

In the pic, if this were on the car, the RED is passenger's side towards the interior and the BLACK is driver's side to the front of the car.

 

Hope this helps.

Jimmy

 

http://www.we-todd-did-racing.com/wetoddimage.wtdr/i=wMjIwODA2NnM0MTNkZmQzMXk1NDE=.jpg

Link to comment
Share on other sites

  • 7 months later...

I was just going to bump this, but I looked at the wire color's for another member, might as well post them here..

 

Black w/ red stripe

Solid green

Solid yellow

Solid light green

Yellow w/ white stripe

Solid Black

 

Like in Jimmy's pic above, the two prongs you use are both black wires..(1black,1black/red)

Link to comment
Share on other sites

 Share

×
×
  • Create New...