View Full Version : ECU - Location, Reset, Codes.

05-19-2002, 12:57 PM
ECU = Engine Control Unit

<span style='font-size:17pt;line-height:100%'>Locations </span>
From Jimwolftechnology.com (http://www.jimwolftechnology.com/)

240SX All D
280ZX All A
300ZX to '89 D
300ZX 90+ C
Truck 86+
Pathfinder 87-95 E
G20 All B
Q45 All Eng.=D, Trans=A
Sentra/200SX 91+ B
Maxima 89+ B

<span style='font-size:17pt;line-height:100%'>How To Reset Your ECU</span>

quote SaintlyCharBoy,May 18 2002,02:46
to reset the ecu:
1) get at it
2) (with key at on position but not running) turn the little screw thingy on the back all the way clockwise, the slot will point to a line on the unit wat 2 or more seconds (if you don't wait you'll just get different codes)
3) start motor
4) turn screw thingy back
5) drive car with no blinky or shiny lights

[edit] the battery thing didn't work on my car, neither did repeatedly turning her on and off

<span style='font-size:17pt;line-height:100%'>How To Read the Codes</span>

quote anthony240,May 18 2002,04:57
There are 2 screws that hold the ECU in place, one at the top just underneath the bottom of the dash, and the other is beneath the ECU to the side of the panel. Once these are taken off, take the dash screw off (right above the first ECU screw). Lift the dash a little bit while wiggling the ECU out, it's tricky but it'll get out.

Turn the ECU around and get to the back of it, you will see a knob with a notch in it beside a caution sticker. Follow directions above, but if you want to know what threw the code, follow this:

-Turn ignition to on position (where most of the lights are on, brake, airbag, etc)
-Turn knob fully clockwise, wait two or more seconds, then turn knob fully counter clockwise
-The service engine light will start blinking, count the blinks. The first blinks are slow, this will represent a first digit.
-There will be a short pause, then the light will blink fast, these blinks will represent a second digit.
-For example, light blinks slow 5 times, and blinks fast 5 times, this is code 55
-If there is only one code, the light will just repeat the code over and over. If there are more, the light will also repeat each code one after the other.
-Once you know what the problem is (or if it's just general maintenance) fix it, and clear the code by starting the car.

<span style='font-size:17pt;line-height:100%'>What the Codes Mean</span>
From ECUtecparts.com (http://www.ecutecparts.com)

11 Crank angle sensor/circuit (1988 to 1990); Crankshaft position sensor (1991 to 1996)
12 Air flow Meter/circuit open or shorted
13 Cylinder head temperature sensor(Maxima and 300ZX models); all others coolant temperature sensor circuit
14 Vehicle Speed Sensor signal circuit is open
15 Mixture ratio is too lean despite feedback control; fuel injector clogged
21 Ignition signal in the primary circuit is not being entered to the ECU during cranking or tuning
22 Fuel pump circuit (Maxima and 1987 and later 300ZX models); all others idle speed control valve or circuit
23 Idle switch (throttle valve switch) signal circuit open
24 Park/netural switch malfunctioning
25 Idle speed control valve circuit is open or shorted
26 Turbo boost
28 Cooling fan
29 Fuel system rich
31 1984 through 1986 EFI models; Problem in air conditioning system; all other models: ECU internal problem
32 1984 through 1986 EFI models; check starter system. All other models: EGR malfuntion (California models)
33 Oxygen sensor or circuit (300ZX left side) - all other models EGR malfunction
34 Detonation (Knock) sensor
35 Exhaust gas temperature sensor (California models)
36 EGR transducer
37 Closed loop control/front oxygen sensor (Maxima)
41 Maxima and 1984 through 1987 300ZX models; fuel temp sensor circuit. All other models: air temperature sensor circuit
42 1988 and later 300ZX models; fuel temperature sensor circuit; all other models: throttle sensor circuit
43 The mixture ratio is too lean despite feedback control; fuel injector clogged (1987 Sentra only): All others; Throttle position sensor circuit is open or shorted
44 No trouble codes stored in ECU
45 Injector fuel leak (California models only)
51 Fuel injector circuit open (California models only)
53 Oxygen sensor (300ZX right side)
54 Short between automatic transmission control unit(TCU) and ECU
55 Normal engine management system operation is indicated
63 Misfire detected - cylinder no. 6
64 Misfire detected - cylinder no. 5
65 Misfire detected - cylinder no. 4
66 Misfire detected - cylinder no. 3
67 Misfire detected - cylinder no. 2
68 Misfire detected - cylinder no. 1
71 Misfire detected - random
72 Catalytic converter malfunction (right side)
74 EVAP pressure sensor
75 EVAP leak
76 Fuel injection system
77 Rear oxygen sensor
81 Vacuum cut bypass valve
82 Crankshaft sensor
84 Automatic trans-to-fuel injection communication
85 VTC solenoid
87 EVAP canister purge control
91 Front oxygen sensor
95 Crankshaft sensor
98 Coolant temperature sensor
101 Camshaft sensor
103 Park/neutral switch
105 EGR and canister control valve
108 EVAP volume control

05-24-2002, 03:26 PM
Ok i checked my ecu and it defenately blinked once slow, then twice fast, But when I first turn the knob to the right nothing happens for two seconds, then the lights blink twice 3 times really fast, the four really fast then five really fast, then there was a second pause then it blank once slow, then twice semi fast! It is an obvious Code 12 (Air flow Meter/circuit open or shorted) but what can i do about it? &nbsp;And does the 2,3, and 4 blinks mean anything?

05-24-2002, 04:34 PM
Excellent Job Dave..

05-24-2002, 08:48 PM
Honestly, MarketPlayer, I have no idea what that would mean.

But in the future post stuff like this in the tech section and just link to the FAQ so this section can stay "answers only" style <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'>
Besides, most people don't check the FAQ much so you likely won't get a reply in any timely manner.

11-03-2002, 12:00 AM
Note: 11 is CAMSHAFT position sensor curcuit. DSC, could you correct that? I just figured it out today (my car threw that code so i looked at the book) <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/confused.gif" border="0" valign="absmiddle" alt='???'> Thanx

Edit: i now looked around the net and it says crank angle/position sensor... Yet my chilton's clearly states that it's camshaft position sensor on all obdII vehicles.... can someone clear this up?

11-04-2002, 10:06 PM
Ok, the ECU resetting pattern is completely incorrect. Well at least for my car (that is 97 240sx). Here is what worked for me:

By orion from FA:
</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">1) Pull the ECU, turn ignition to ON but don't start engine
2) Turn the screw full clockwise, hold 2 seconds, turn back
3) read the codes
4) Repeat step '2' to erase codes, start car to store them</td></tr></table><span id='postcolor'>