Battery Drain on ECU fuse PLEASE HELP!!!

[Cpt_Impossible]

I have a 1990 240sx Coupe with RB20DET swap and Have been dealing with a battery drain for some time now.

Basically when the "Eng Control" (which I assume is the ECU) fuse is in, the battery shows 0.50Amps being pulled when I use an ammeter between the post and positive cable. When it is removed, I show 0.05Amps. There are two green relays behind the ECU. Unplugging either of them stops the drain back down to 0.05Amps. Only when they are both connected does it drain. I tried switching the relays out for the identical lookign EFI ones under the hood with the same result. I bought a clamp on style ac and dc Ammeter to start trackign down which wire on the ECU but the craftsman 60 dollar one I bought appears to be junk and is wildly innacurate. I am trying to avoid having to cut ecu wires to track down what is causing the problem.

Battery (optima yellow top) tests fine and was switched with a standard one just to be sure with the same results.

Alternator was just replaced to rule it out.

Starter was disconnected and problem persisted.

PLEASE PLEASE PLEASE someone help me, I havent been able to daily drive my RB since July because I can't leave it on the street with the the battery connected unless I unplug the ECU every time so it makes it really hard to set the alarm and every time I start the car the ecu has just been reset. This is driving me nuts and I cant find the problem. Also if anyone near SeaTac has an rb20 ecu I can borrow for 2 hours to rule out that my ecu isnt fused somewhere that would help.

So I did some more testing and heres what I have found:

Near the Battery there is a fat grey plug. If this plug is undone, ECU fuse current drops to 0 amps. The specific connection in the plug that is drawing amperage is the solid red wire. If this plug is undone, the ECU fuse doesn't get power.

For the two plugs that go into the two relays behidn the ECU. I had marked one of them "1" and the other "2". 2 being the one with thinner wires:

-Orange-White w/ Black stripe-White w/ Black stripe-Black w/ White stripeThe two White w/ Black stripe wires both see 0.06volts when the ECU fuse is unplugged and 12volts when it is plugged in.

When using the ammter to jump the ECU fuse, the TPS sensor is pulling 0.05Amps. (When it is unplugged thats how much the ammeter goes down)

When using the ammeter to jump the ECU fuse, the MAF sensor is pulling 0.11Amps. (When it is unplugged thats how much the ammeter goes down)

I tested how much voltage each pin on the ECU harness was showing with the harness unplugged fromt he ECU. The pins that showed voltage were:

3: 0.26v7: 0.04v16: 7.30v26: 0.01v27: 0.39v41: 0.03v42: 0.03v45: 2.63v51: 0.03v52: 0.03v58: 12.0v59: 12.0v101:12.0v103:12.0v105:12.0v109:12.0v112:12.0v114:12.0v

Keep in mind this is an RB20DET manual ECU.

Ecu pinout: rb20det eccs control unit pin layout.1 Ign signal (power transistor) Cyl #12 Ign signal (power transistor) Cyl #53 Ign signal (power transistor) Cyl #35 engine. A/T control input signal (bt1)6 Sub electrical fan relay (engine temp switch)7 Tacometeter speed signal9 AC relay (AC cut signal)10 Ground (ign signal system)11 Ign signal (power transistor) Cyl #612 Ign signal (power transistor) Cyl #213 Ign signal (power transistor) Cyl #414 engine. a/t control input sigal (bt2)15 engine. a/t control input sigal (bt3)16 ECCS relay18 fuel pump relay19 Power steering switch20 Ground (ignition signal system)21(RX) Receive (control unit data reception)22 (TX) Transmit (data sent from control unit)23 Detonation sensor 1 (cyl 1-3)24 Detonation sensor 2 (cyl 4-6)26 Air flow meter ground27 Air flow meter intake air quantity signal28 Engine temp sensor29 Exhaust gas sensor30 Sensor ground (throttle sen, ENG temp)31 clock (synchronization signal)32 Monitor and check lamp (red)38 Throttle opening output41 Crank angle sensor (120degree signal)42 Crank angle sensor (1 degree signal)43 Ignition switch START signal44 Neutral switch45 Ignition switch (IGN)46 AC switch47 (CHK) Check (diagnosis activation)48 Throttle sensor power supply49 Control unit power supply50 Ground (control unit)51 Crank angle sensor (120 degree signal)52 Crank angle sensor (1 degree signal)53 Vehicle speed sensor54 Throttle valve switch (idle connection pt)56 Throttle sensor output signal57 Throttle valve switch power supply58 Battery power supply59 Control unit power supply60 Ground (control unit)101 Injector #1103 Injector #3104 Fuel pump terminal voltage control output105 Injector #2 107 Injector ground108 Injector ground109 Injector power supply110 Injector #5112 Injector #4114 Injector #6115 exhaust gas sensor heater ground116 injector ground
Modified by Cpt_Impossible at 9:09 PM 1/7/2007

[Cpt_Impossible]

I'm half tempted just to label the thread "New S13 Altezza's on Ebay" just to get someone to actually help me...

[jdmser]

Check voltage at pin 58 and pin 59. Voltage at pin 58 should be a constant 12v and pin 59 should be a switched 12v coming on with the key.

[ISUJinX]

Do you have ignition relays like the RB25? If you do, and the relays are wired incorrectly the car may think that the key is in the "on" position all the time. IE, that would be like running the ignition power to the start relay instead of the start switch.... I dunno much about the RB20 wiring, sorry man.

[Darius]

Sounds to me like your ECU is constantly receiving power instead of receiving switched "ON" power. It could be a wiring problem, but it sounds more like a relay problem (ECCS). Either way, it has to do with the wiring of the relays (power supplies or grounds) or the relays themselves. Check where your ECCS relay power supply is coming from. (i.e. where it is getting power from the dash harness)

If you plug your harness back into your ECU, do you get voltage readings at the CAS, MAF, and all the other sensors on the motor? If so, not only are you draining your battery down, but heating up the senors and creating unnecessary wear and tear.

[Cpt_Impossible]

ya 58 and 59 are both seing 12v with the car off and the ecu unplugged. Would that suggest there is a problem with ignition or turbo timer? I am using an easy harness on the timer so I didnt have to mess with any lines there as far as cutting and splicing.

[Cpt_Impossible]

Need a quick answer!

Which one is the ECCS Relay? Is that one of the ones behind the ECU? Because I dont see anything labeled eccs...

[Darius]

Yes there are two near the ECU and one is the IGN and the other the ECCS relay. I'm pretty sure 59 shouldn't have power when the car is off. Check the on the ECCS relay. Something is causing current to flow through it and thus close the relay circuit which powers your ECU all the time and drains your battery.

[Cpt_Impossible]

cool, thanks Im heading to dealership right now to rule out the relays and just replace them.

[Cpt_Impossible]

Anyone got any KY? I just got charged $62 for the pair at Nissan!

[Cpt_Impossible]

and apparently that was money down the drain, didnt fix the problem. They are nice and shiny though...

[Cpt_Impossible]

OK, I think I found my problem...

The swap shop looks like it's to blame.

Pin *49*, 59, and 109 are all clamped together further down the harness with some other wires. I don't know why. Anyone know where pin 59 should go?
Modified by Cpt_Impossible at 7:02 PM 1/8/2007

[Cpt_Impossible]

So there are 6 pins total clipped together. 3 from the ECU, 2 from the mainharness, and one from the sub harness inside the main harness that is in a fat grey wire (this one is a little bit thicker).

One of the ones from the ecu sees 2.33 volts when the ignition is off and 12v when the ignition is on.

One of the ones from the main harness sees 12v when the ignition is off but 0v when the ignition is on. I am totally lost here as to what the hell is going on...

[Cpt_Impossible]

So 49, 59, and 109 are the three coming fromt he ECU. 49 and 59 are both called "Control Unit Power Supply." 109 is the "injector power supply."

I looked at a wiring diagram and 49 and 59 should be connected together and then to pin (3) of the ECCS relay.

109 should be connected to the six inector powers and then to pin 4, and pin (5) and (1) of the ECCS Relay

[skillzilla]

Which write up did you use to do your swap? Did you wire your constant and switched power by the ecu or by the passenger headlight?

[Cpt_Impossible]

A shop did my swap and harness so this is all suprises to me.

[Hype]

Sorry for digging up this old thread, but I have had this problem for QUITE some time, but my car is a stock 92 5spd...

.5 amp draw with key OFF that drops to normal (~30mA) when that fuse is pulled or the ecu is unplugged. I searched to see if anyone had recently found a solution, but all I came up with is this thread and my own, to which no one replied

[skillzilla]

Heres a quick test: if your key is off and you have power going to your injectors, coilpacks, CAS, ignitor, etc, then you have the switched power lead running to a constant power source, or you have a short in the upper harness between the switched power wire and the ecu. Check that first.

[Cpt_Impossible]

Well I found a solution to mine. I didnt find the original source but a fix. With mine, the orange wire going to the ecu from the ecu relay, one of the two green ones in the kickpanel, the wire splits into two and goes to both relays on mine. That wire was showing 7 volts so I split it at the Y. I found that if any two of the three directions were connected, there was no problem, but if all three (ecu, ecu relay, other relay) were connected the drain appeared. I made a switch that connected the ecu with the two relays and turn it off when I turn off the car. That fixed it. I then found that the switch was pointless as the car starts and runs fine with the switch off.

[gbaz77]

was just going to say the same thing to fix. i did the exact same thing to my car. glad it worked for you.

[Cpt_Impossible]

You mean the relay wire? (Orange)