GROUNDS And O2 sensors

[MustangOwl]

I’m trying to track down what may be a grounding issue for my ECU (or my ECU is faulty… joy). The brown-with-black wire running out of E1 on my ECU looks like it snakes through the bigger harness into the engine bay, then down towards the starter (where i can see it / it’s out of the insulation at this point), past that and then it looks like up over the transmission and clips into the O2 sensor.

What am I missing? Where should the wire connect to a ground?

side note: I think I ordered incorrect O2 sensors (1989 ones and not 1990 ones). Anyone know what that would do to the ECU?

**Still tracking a crank no-start with no CEL when the key is in “on” issue**
**1990 FJ62, 11/89 manufactured date**

 

[InfiniteZ]

Did you ever find a solution?

I’m running into the same issue
Crank, no start, no cel

Replaced starter due to power surge, replace batt (fell to 4v under load.)Fusible link, EFI and COR found ok per FSM. Undid my wire harness up until where it breaks off to the diag box to track E1 from ECU and got continuity on ground but no CEL.

The brwn/blk wire leads to that bundle behind the engine. The lead was mounted roughly under the cold injector on intake manifold.

 

[Lead Head]

What do you mean "power surge"? There is really no such thing as a "power surge" in automotive vehicles unless your alternator goes full-field or it gets hit by lightning.

If you don't have a CEL, there are only 5 possibilities:
1) ECM has no "BATT" or B+ power
2) ECM is not receiving IGSW signal
3) ECM has no grounds
4) ECM has failed
5) Bulb has burnt out

Start by checking for power at IGSW, BATT and B+ on the PCM with the key on.

1988 FJ60 Wiring Diagrams - Land Cruiser Tech from IH8MUD.com

1988 FJ60 Wiring Diagrams - Land Cruiser Tech from IH8MUD.com

www.ih8mud.com

 

[InfiniteZ]

What do you mean "power surge"? There is really no such thing as a "power surge" in automotive vehicles unless your alternator goes full-field or it gets hit by lightning.

If you don't have a CEL, there are only 5 possibilities:
1) ECM has no "BATT" or B+ power
2) ECM is not receiving IGSW signal
3) ECM has no grounds
4) ECM has failed
5) Bulb has burnt out

Start by checking for power at IGSW, BATT and B+ on the PCM with the key on.

1988 FJ60 Wiring Diagrams - Land Cruiser Tech from IH8MUD.com

1988 FJ60 Wiring Diagrams - Land Cruiser Tech from IH8MUD.com

www.ih8mud.com

Sorry, I get my aviation jargon mixed with car mechanics. I meant the power draw from the starter was excessive then it would bog down, but also found out my batt had a dead cell. Would read 12.6v and drop to 4 at crank.

As for testing with key on, I haven’t touched it in over a month but from what I remember….

I checked 4 of the possibilities that you’ve mentioned.
Tested voltage to B+ and it was good.
Tested the bulb and it was good per FSM. Also verified by grounding the W on the ECM, it lights up no issue. Because of the grounding on the W checked the E1 per FSM troubleshooting and chased the grounds down the harness up until where I previously mentioned (Ys off to Diag Box) wires were good. Cleaned off most grounds just to be safe.
Tested a spare “working” (to my knowledge) ECM and no change. Opened my old one to inspect circuitry and looks fine.

I roughly wiggled some of the ign system wires to see if anything changed but nothing. I’ll look into that next.

Per the tree the ignsw would have been an issue if the light didn’t come on after grounding W. But it did and so that’s where I had a head scratcher for the past month. Definitely will now be taking a look at that next. If you have any other suggestions that would be greatly appreciated

 

[Lead Head]

Sorry, I get my aviation jargon mixed with car mechanics. I meant the power draw from the starter was excessive then it would bog down, but also found out my batt had a dead cell. Would read 12.6v and drop to 4 at crank.

As for testing with key on, I haven’t touched it in over a month but from what I remember….

I checked 4 of the possibilities that you’ve mentioned.
Tested voltage to B+ and it was good.
Tested the bulb and it was good per FSM. Also verified by grounding the W on the ECM, it lights up no issue. Because of the grounding on the W checked the E1 per FSM troubleshooting and chased the grounds down the harness up until where I previously mentioned (Ys off to Diag Box) wires were good. Cleaned off most grounds just to be safe.
Tested a spare “working” (to my knowledge) ECM and no change. Opened my old one to inspect circuitry and looks fine.

I roughly wiggled some of the ign system wires to see if anything changed but nothing. I’ll look into that next.

Per the tree the ignsw would have been an issue if the light didn’t come on after grounding W. But it did and so that’s where I had a head scratcher for the past month. Definitely will now be taking a look at that next. If you have any other suggestions that would be greatly appreciated

View attachment 4078690

That's a very rudimentary flow chart and not at all comprehensive. Look at some of the schematics I linked.

You need to verify that "BATT" has +12v at all times, key on and off. You need to verify that when you turn the key on, the IGSW signal at the PCM gets +12v.

You then need to verify that the M-REL gets is also at +12v (this voltage is provided by the PCM). This will pull in the main EFI relay which will then energize B+.

Finally, there are a lot more grounds than just E1. There is E01 E02 and E11 as well as E2. Check for ground continuity on all of those.

 

[InfiniteZ]

That's a very rudimentary flow chart and not at all comprehensive. Look at some of the schematics I linked.

You need to verify that "BATT" has +12v at all times, key on and off. You need to verify that when you turn the key on, the IGSW signal at the PCM gets +12v.

You then need to verify that the M-REL gets is also at +12v (this voltage is provided by the PCM). This will pull in the main EFI relay which will then energize B+.

Finally, there are a lot more grounds than just E1. There is E01 E02 and E11 as well as E2. Check for ground continuity on all of those.

I actually just got into it today. I don’t remember everything I did but here it goes….
Batt is at 12.7V
+B and +B1 both showed 12.4V
IGSW showed 12.4V
E1 was 12.5V same as Batt
Tested Neg Post to E1 Voltage, read 0.00V
For the M REL test with black on Batt neg post and Red on Pin I got 10.9V
0.00v with black on batt neg and red on e2 pin with key on
Test light was bright and stable with it clipped to batt neg and probing igsw
For the Sta reading I got 0.00v with black lead on neg batt post and red lead on STA pin with key on no cranking
With red on nsw pin and black on neg batt post and key on reading is 0.00v with key off it remained at 0.00v both in Park and neutral
Jumped NSW to E1 and keyed on CEL light did not come on
Jumped the T and E1 on the ECU pin and nothing changed. No cel light
With key off. I set my multimeter to 2k ohms. It read from .000 on the E01 and E02 jumper.
With those pins still jumped got a jumper from batt neg post to them and keyed on. No cel light


What I just realized is you saying the MREL needs to be at 12? I didn’t get that it might have spiked to it or I might not written in down properly but I have 10.9v on my notes for it. I’ll have to check it again but even removing the relay and bench testing it passed the inspection

 

[Lead Head]

I actually just got into it today. I don’t remember everything I did but here it goes….
Batt is at 12.7V
+B and +B1 both showed 12.4V
IGSW showed 12.4V
E1 was 12.5V same as Batt
Tested Neg Post to E1 Voltage, read 0.00V
For the M REL test with black on Batt neg post and Red on Pin I got 10.9V
0.00v with black on batt neg and red on e2 pin with key on
Test light was bright and stable with it clipped to batt neg and probing igsw
For the Sta reading I got 0.00v with black lead on neg batt post and red lead on STA pin with key on no cranking
With red on nsw pin and black on neg batt post and key on reading is 0.00v with key off it remained at 0.00v both in Park and neutral
Jumped NSW to E1 and keyed on CEL light did not come on
Jumped the T and E1 on the ECU pin and nothing changed. No cel light
With key off. I set my multimeter to 2k ohms. It read from .000 on the E01 and E02 jumper.
With those pins still jumped got a jumper from batt neg post to them and keyed on. No cel light


What I just realized is you saying the MREL needs to be at 12? I didn’t get that it might have spiked to it or I might not written in down properly but I have 10.9v on my notes for it. I’ll have to check it again but even removing the relay and bench testing it passed the inspection

I'm a little confused about how you're testing things. You say E1 measured 12.5v, then later say it measures 0 volt.

At the ECU connector, with the ECU connected and the key ON, you should have the following voltages:

BATT to BODY/BATTERY NEG: 12v
+B to BODY/BATTERY NEG: 12v
IGSW to BODY/BATTERY NEG: 12v
M-REL to BODY/BATTERY NEG: 12v
VCC to E2: 5V
E01 to BODY/BATTERY NEG: 0v
E02 to BODY/BATTERY NEG: 0v
E11 to BODY/BATTERY NEG: 0v
E1 to BODY/BATTERY NEG: 0v


Don't even bother worrying about STA or trying to crank it. If the CEL is not coming on, the computer is not powering up.

 

[InfiniteZ]

I'm a little confused about how you're testing things. You say E1 measured 12.5v, then later say it measures 0 volt.

At the ECU connector, with the ECU connected and the key ON, you should have the following voltages:

BATT to BODY/BATTERY NEG: 12v
+B to BODY/BATTERY NEG: 12v
IGSW to BODY/BATTERY NEG: 12v
M-REL to BODY/BATTERY NEG: 12v
VCC to E2: 5V
E01 to BODY/BATTERY NEG: 0v
E02 to BODY/BATTERY NEG: 0v
E11 to BODY/BATTERY NEG: 0v
E1 to BODY/BATTERY NEG: 0v


Don't even bother worrying about STA or trying to crank it. If the CEL is not coming on, the computer is not powering up.

BATT to BODY/BATTERY NEG: 12.4
+B to BODY/BATTERY NEG: 12.4
IGSW to BODY/BATTERY NEG: 12.4
M-REL to BODY/BATTERY NEG: 10.9
VCC to E2: 0.03
E01 to BODY/BATTERY NEG: 0
E02 to BODY/BATTERY NEG: 0
E11 to BODY/BATTERY NEG: 0
E1 to BODY/BATTERY NEG: 0

So either my EFI relay is bad even though it passed the bench test a month ago. Or according to the VC / E2 readings the throttle pos sensor is bad?

 

[Lead Head]

BATT to BODY/BATTERY NEG: 12.4
+B to BODY/BATTERY NEG: 12.4
IGSW to BODY/BATTERY NEG: 12.4
M-REL to BODY/BATTERY NEG: 10.9
VCC to E2: 0.03
E01 to BODY/BATTERY NEG: 0
E02 to BODY/BATTERY NEG: 0
E11 to BODY/BATTERY NEG: 0
E1 to BODY/BATTERY NEG: 0

So either my EFI relay is bad even though it passed the bench test a month ago. Or according to the VC / E2 readings the throttle pos sensor is bad?

The computer provides the M-REL power, which then turns on the Main EFI relay, providing +B power to the ECU and various solenoids/actuators. Since you have +B, I'm pretty sure the relay is engaging and working fine.

VCC to E2 reading 0.03v is bad since everything else checks out fine. That indicates you either have a short to ground in your VCC line (which powers the air flow meter and the TPS), or the 5v regulator inside the ECU has failed. The main CPU and other chips will also be running off 5v.

I'd start by unplugging the TPS and AFM, and see if the computer comes back up (CEL on). If it does, one of those things has gone short internally. Plug one in at a time and see which it is.

If it still doesn't come back up with both uplugged, I suspect you have a short somewhere. Disconnect the connector with the VCC and E2 wires, and then measure the resistance across those wires

 

[InfiniteZ]

The computer provides the M-REL power, which then turns on the Main EFI relay, providing +B power to the ECU and various solenoids/actuators. Since you have +B, I'm pretty sure the relay is engaging and working fine.

VCC to E2 reading 0.03v is bad since everything else checks out fine. That indicates you either have a short to ground in your VCC line (which powers the air flow meter and the TPS), or the 5v regulator inside the ECU has failed. The main CPU and other chips will also be running off 5v.

I'd start by unplugging the TPS and AFM, and see if the computer comes back up (CEL on). If it does, one of those things has gone short internally. Plug one in at a time and see which it is.

If it still doesn't come back up with both uplugged, I suspect you have a short somewhere. Disconnect the connector with the VCC and E2 wires, and then measure the resistance across those wires

You are a legend.
I unplugged 1 at a time starting with the TPS since I had previously checked the AFM and it met the FSM criteria.
Turns out the TPS is fine but with the AFM, I thoroughly checked, unplugged the CEL shines brighter than ever before.
Now the real question, would you suggest even try and tinker with it or just replace? I’m not one to just throw on new parts at it, but I know it’s hard to come by these parts and genuinely impressed everything so far looks OEM sitting with 290k on the ODO.

I appreciate everything and I apologize that I hijacked this thread too haha

 

[Lead Head]

On the AFM, check the resistance between pins 3 and 4 (green-red and brown-black). Also check the resistance between Pin 3 (green red) and body/chassis ground.

I would also inspect the wires to the AFM connector to make sure they aren't chaffed through and shorted.

 

[InfiniteZ]

On the AFM, check the resistance between pins 3 and 4 (green-red and brown-black). Also check the resistance between Pin 3 (green red) and body/chassis ground.

I would also inspect the wires to the AFM connector to make sure they aren't chaffed through and shorted.

Just did the check you mentioned and i think it solidified the AFM being the issue

Got 0s for Pin 3 to 4 even when moving the flap.
Also checked the G-R to Ground and got a 192 reading.

 

[Lead Head]

Just did the check you mentioned and i think it solidified the AFM being the issue

Got 0s for Pin 3 to 4 even when moving the flap.
Also checked the G-R to Ground and got a 192 reading.

Yeah that would do it. Not sure how that could happen though. If you're feeling adventurous, you can use a knife to cut the silicone and pop the lid on the AFM's resistor/switch area.