one simple question...#8 and #9 when jumpered/grounded do not need the inginition turned to on for the fans to work?

 

93-95s must have the ignition ON (engine does not have to be running).

 

Hi Shoebox,

I put the key to "on" for the ignition.

1. I grounded the H prong from the C100 harness on the "fan side" and the LH fan came on LOW.
2. I grounded the J prong from the C100 harness on the "fan side" and the LH fan came on HIGH.
3. I grounded both H and J prongs from the C100 harness on the "fan side" and both the RH and LH side fans came on at HIGH.
4. I grounded the prong on the C100 harness from the "PCM SIDE" but nothing happened...which makes sense if the PCM is sitting there unattached electrically from the fans because the C100 harness is disconnected.

Q1?The PCM however was sending information of 5volts to the water pump sensor when that was checked. Does this rule out the possibility of the PCM being the problem because of the DVM check at the water sensor?

Q2? The relays were checked in the fog light relay position. Both fans came on when the water pump sensor was removed. Does this mean that the relay position for the fans would be grounded properly. Or is there a possibility of the ground on one of the relay positions not working properly?

Q3? Or is this simply a matter of fixing the PCM? As I worked my way backwards with the steps you provided me and everything was fine up to the PCM...which would indicate the PCM is the problem? If so how do I "re-flash" the PCM. I removed the PCM fuse in the U/H box for 15 seconds or longer...is this how to "re-flash" the PCM memory? Nothing changed though after doing this. To "re-flash" the PCM do you have to do something within the PCM itself? Or is there a way to check the PCM if I open it up?

Thank you!

 

Grounding back toward the PCM won't test anything. The PCM is what sends the ground to the fan relays to turn them on, so if anything, you should be looking for a ground from the PCM when it is time for the fans to come on.


Since your fans come on when you removed the ECT, you have already proved that the circuitry from the PCM to the fans is ok. What you really need is that scanner to verify what commands the PCM is putting out.

You cannot flash the PCM by just removing the fuse. The flash memory is non-volatile and will remain. The volatile memory is erased when you pull the fuse, but that is mostly just what the computer has learned about fuel delivery.

I cannot recommend strongly enough about having a scanner to help you.

 

Hi,

I have scanned the engine finally. I made the converter from the schematic that AKM cables has on his website...hooked it up to my laptop and OBDII connector (car is OBDI 1995). First time doing this and it worked...

What should I be looking for to finalize a diagnosis as to why the coolant fans are not coming on. I scanned using the TTS Datamaster.

Thanks!
Peter

 

Watch the coolant temp and also the fan relays (you can select different parameters to watch on the RH side of the Datamaster display by double clcking the cell).

 

Hi,

What notation are they using in Datamaster for the fan relays? I clicked on the right hand cell and do not see fan relay listed...it must be under something else...?

Thanks

 

Hi Shoebox,

I figured out where and what you were talking about...the top RH box with 12 cells...I was clicking on the lower box for the graph information.

I have found out the fan relay #1 comes on at 227.3F coolant temp...the coolant temp guage for dash is the same as what datamaster is reading...the fan relay #2 does not come on...

Even though FR#1 comes on at 227F the actual fan itself does not start up...

The thermostat is a Hypertech 160F.

WHat do you think is going on?

 

The relay is commanded to come on or is the relay actually energized?

 

Now you know the PCM is commanding the fan on at the right temperature. Check D2 with fan relay 1 removed to see if it is getting a ground from the PCM (use a high impedance meter). If not go back to C100 to see if the ground is there.

With all your other tests it would seem like the fans should come on.

 

Hi Shoebox,

My multimeter has four settings 20M, 200K, 2K, and 200. When you say Hi Impedance which setting would you recommend?

Where do I place the leads...ie. red where and black where...stupid question but I am just learning about all this stuff...for both the D2 position and the C100...

And what reading should I look for on the meter?

Thanks!

 

High impedance meter-not scale. Most good digital meters have 10megohm impedance or better and that is what is required to not blow up your PCM.

If you are going to look for ground, just set it to 2k scale, attach one lead to ground and the other to whatever you are testing.

There are fan schematics on my website. I wish I could teach a class on reading schematics, but it is beyond what can be done here.

 

1. I hold the lead to D2 and the other lead to ground and DVM (set at 2K) reads "1"...what does this tell us...

2. When I hold the lead in the C100 J slot (drk green wire) and the other lead on the chassis ground it reads "1" as well...

I have been looking at the schematics you have on your website...as well as the Haynes manual.

If the ground is bad at the relay do I just rewire it or is there more involved?

 

Is this with the fan relay indicated as ON?

Which side of the connector at C100 are you probing (fan relay side or PCM side)?

What is the reading when you touch the leads together? Do you have the meter set to read resistance?

 

It is with the fan relay #1 indicated as on (as the Datamaster program specifies it is signaling FR#1 to come on at 226F. The key is out of the ignition.

I'm probing the Fan relay side on C100 "J" with ignition off. I hold the lead on that probe and the other lead on the car chassis.

The meter is set to 2K reading Ohms resistance. The reading when I hold it on the D2 position (for FR#1 and the car chassis) is "1" or open/shorted (?). This is of course with the C100 still connected to the PCM.

And on c100 "J" is also reading "1" when I probe the FR side of the connector (which I guess makes sense if the fan relay has been removed...should I be checking the ground from the PCM side at C100?)

I think I'm getting close to finding the problem...