[QUOTE]Originally posted by Squeezer
you'd take a dump if you ever had to replace it.

 

REDMX5,

I checked out the little black box and all it does is send battery voltage to the ECU via a 7.5 amp relay. There is no current shunt inside it, just a heavy metal strip.

The manual also states in the diagnostics that that input expects to see battery voltage not 5 volts.

The blue wire/black wire to the solenoid supplies switched battery volts from the ECU ( will lose around 0.7 volts over the switching transistor), with the black going to earth. The reason for the resistor is purely to provide some pull down load in place of the solenoid coil as I suspect the ECU will also check to make sure the solenoid is connected.

Speedracer.

 

Hi Chris,

Now I'm confused. On page 11-146 the manual states that we should measure "approx. 5V" between pins 1 and 2 on the on the AIR pump current sensor 3p connector. I don't see 12V anywhere in that part of my manual. Apparently we're looking at different things, but I can't figure out how or why.

Give me a page number so I can figure out what you're looking at.

Thanks,

RED


[QUOTE]Originally posted by chris_barry
REDMX5,

I checked out the little black box and all it does is send battery voltage to the ECU via a 7.5 amp relay. There is no current shunt inside it, just a heavy metal strip.

The manual also states in the diagnostics that that input expects to see battery voltage not 5 volts.

The blue wire/black wire to the solenoid supplies switched battery volts from the ECU ( will lose around 0.7 volts over the switching transistor), with the black going to earth. The reason for the resistor is purely to provide some pull down load in place of the solenoid coil as I suspect the ECU will also check to make sure the solenoid is connected.

 

I'll dig up the page number.

I was looking at the air pump diagnostic flowchart.

I took the black box with the 7.5amp fuse apart and all it has was a large metal strip between the input/output and the output connected to this strip. I couldnt measure any resistance over this strip.

 

REDMX5,

Had a look at my manual. I only copied the pages applicable to the RHD Australian model so only have those page numbers. I also left out lots of sections that werent applicable to my application.

The current shunt (ELD) you mention is on the main supply to more than the air pump. It also measures current to the power steering, headlamps and ABS. ( plus I think the rest of the cars electrics). They seem to tie the idle control, voltage regulator and current used together with the ECU.
I'm not sure if removing the current for the air pump will throw a CEL from the current shunt(ELD) signal changes alone.

Futher down the wiring there is the air pump relay which has the blue/black wires. This is controlled by the ECU. disconnecting this may throw a CEL as the ECU will not see a load on this channel.

Between the relay and the pump there is a single wire connector to a small box with a 7.5amp relay. According to 11-A-147 of the manual this wire sees battery voltage when the air pump is running. This battery voltage signal is sent to the ECU.

My suggested modification was to allow the removal of the air pump main relay and all electronics downstream of this. The resistor over the relay control wires and connection of the green single wire should trick the ECU to thinking the airpump relay is still there an working. The donor car I used had the FL corner completely destroyed so I dont have any of the air pump relay or wiring intact.

As for the effect of the current shunt in the underbonnet(hood) relay box with the air pump removed I'm unsure of the effect of removing the air pump. If the other devices are also drawing current throught this same Electronic Load Detector (ELD) device I wouldnt have expected a CEL from the ELD device.

I'll have more info in the next few weeks when I get a chance to wire up my clubman. I need to get a radiator on it so I can run the engine for more than a few seconds at a time.

Speedracer.

 

Hi Chris,

I hope you are enjoying trying to sort this out as much as I am. Normally I'd be sorting it all out on my own, as time permitted, and it's really nice to be working through it with some company. This ECU is quite different than tuning with SU's and Webers.

I hadn't realized that you were down-under. Since I'm in the US, our cars may not have identical systems.

The black-box I'm looking at in the US spec manual is referred to as "the AIR Pump Electrical Current Sensor." It has two connectors, a 2P and a 3P. The 2P connector is suppose to measure battery voltage between pin 1 and ground. With the ignition off, a short is measured between pins 1 and 2. This *appears* (I do not have a schematic available) to be connected to the AIR Pump relays (there is a large relay, and a small relay). The 3P connector goes to the ECU. We're supposed to measure 5 volts between pins 1 and 2. Pins 2 and 3 go directly to the ECU. I can't see how any other circuits are connected to this box, so perhaps our systems differ in this area.

On US cars, the Large AIR Pump Relay P2 connector has a white/red wire and a white/green wire. The Small AIR Pump Relay has a black wire and a blue wire. Since I haven't found a schematic yet, I have no idea why two relays are used.

According to my manual, 11-147 (I have no 11-A-147) the ECS sends 5-volts to pin 24 of the ECU when pins 2 and 3 of the APECS 3P connector are shorted. That's why I thought you were using the resistor to drop the 12v down to 5v. Perhaps the US model uses 5-volt logic while the "A" model uses 12-volt logic??? I assume that I'm understanding properly, and that your manual shows 12v going to ECU pin 24? (It could also be that our pages are numbered differently.)

I'm wondering if the ECU checks for both the on and off condition. If it does, making it look like the pump is running constantly won't help. I'm also wondering if the ECU might not throw a CEL when the secondary O2 sensor detects the too-slow cat warm-up. Just don't have a good feel for how sophisticated the ECU algorithms are, and don't have any logic diagrams or code to examine (and not even a cotton-pickin' wiring diagram).

At some point I'll monkey around with the AIR system a little and figure out what it takes to fool the ECU, but I want to have a better feel for how it operates before I start messing with the ECU inputs. I think 5v at pin 24 will do the trick, but it may have to be switched on and off when the pump would normally go on and off. Should be able to do that with a relay and the signal that powers the pump relay. The one thing I want to avoid at all cost is putting a 12v signal on a 5v logic line.

The US cars may be different. I might just be overlooking it, but it seems that our cars use the AIR pump current sensor only for the AIR current. If your setup is measuring a sum of currents it doesn't seem that it could tell the difference between a heavier or lighter power steering load and the AIR pump being on or off. Your car might not even throw a CEL if you disconnect the pump.

Excellent. I stay pretty busy too, so it may be a few weeks or even longer before I have the time to get out and play around with the system to see how it really works. I also need to spend some more time studying the manual. I suspect that the "A" in your manuals page numbering scheme might indicate country specific information. In any event, if nobody else comes up with full and complete information on the system, I'll post the info when (and if) I figure it out. Then we can compare notes and see how the cars in Oz vary from the cars here in the US.

Who'd have ever guessed that something so simple could be so complex?

RED

 

REDMX5,

I looked through my manual and in the back there was a picture of the air pump current sensor as you described. It looks like there is a difference between the US and Aus market electronics.

I would find a way to put a resistor divider in place of the air pump current sensor. Use a 2K wire wound poteniometer over the +12v and gnd. By adjusting the pot you can vary the output to the sensor. ( measure before/after with a voltmeter). The approx 1K between the +12v and sweeper of the pot will limit the current to the ECU and hopefully avoid any burnouts.

I'm amazed at the amount of feedback in this cars electronics. Lots of systems are interconnected. The instrument panel looks after lots of things such as a speed output to the ABS, power steering, hood etc. It also controls the wiper speed, fog lamps and day running lights.

I'll keep you updated on my progress even though my hack sounds like it wont suit your car.

Speedracer.

 

Here are the answers on the Mugen ECU:

[QUOTE]Originally posted by PsychoBen

 

Isn't the price on the Mugen ECU almost the same price as the EMS???

 

Chris barry and Red MX5, have you guys got any fix for this yet?

I am planning to take out my air pump this weekend. I got an aem ems and don't have to deal with the cel at this stage. However, I like to fix it while the bumper is off. Just in case I get "defected" and have to restore the car to stock and put the oem ecu back (temporarily ), the check engine light wont come on me.