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Discussion Starter · #1 ·
Hello,

I am super confused as to what is going on. 1996 RAV3 4x2 Manual.

Car works fine for a while then it will start blowing the EFI fuse. It blows as soon as you turn the ignition on and won't allow the car to start. I pulled up the wiring diagram and have disconnected all the sensors that seem to be on the circuit. Also unplug at lot of other sensors. Turn the ignition and the fuse is still blowing. I also move wiring harnesses to see if those are spots for the short. Same result, EFI fuse still blows out.

The only fix I have found for this is to unplug the ECM. Then turn the key and it will stop blowing the fuse. Reconnect it and it goes back to normal, car will start. Will not blow the fuse for another while, couple days. Is that a sign of a shorted ECM? I have also left the battery unplugged overnight and that doesn't get rid of the fuse blowing until I unplug the ECM.

Any insight on what this maybe would help me as I am so confused. Debating just replacing the ECM to see if that does it.

Thanks.
 

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The engine computer (ECM) rarely fails. Below are the tests I would do first.

Look at the wiring diagram on PDF page 170 of the attachment. Find the EFI fuse near the bottom of the diagram.

On the wiring diagram, follow the wiring downstream of the EFI fuse to (1) the ECM; (2) the EFI Main Relay; (3) the Circuit Opening Relay; and (4) the fuel pump. Notice that a signal from the ECM is what causes the Circuit Opening Relay's coil to be energized.

The Circuit Opening Relay is in the relay box near the driver's left knee. The EFI Main Relay is in the relay box in the engine bay. As needed see the two, one-page attachments showing each relay's location.

First Test:
1. Remove the EFI Main Relay.
2. Make sure the EFI fuse is brand new and installed.
3. Turn the ignition key to the "On" position (engine off).
4. Does the EFI fuse blow? Report back here.
5. Remove the ignition key.
6. Re-install the EFI main relay.

Second Test:
1. Remove the Circuit Opening Relay.
2. Make sure the EFI fuse is brand new and installed.
3. Turn the ignition key to the "On" position (engine off).
4. Does the EFI fuse blow? Report back here.
5. Remove the ignition key.
6. Re-install the Circuit Opening Relay.

Third Test:
1. Remove the Circuit Opening Relay.
2. Remove the rear, left seat (four, 14mm bolts). Lift the carpet.
3. Remove the four phillips screws holding the now exposed access panel in place.
4. Remove the access panel. You will see the top of the fuel pump assembly.
5. Disconnect the five-wire connector on the top of the fuel pump assembly.
6. Make sure the EFI fuse is brand new and installed.
7. Jumper pins 3 and 5 of the Circuit Opening Relay.
8. Turn the ignition key to the "On" position (engine off).
9. Does the EFI fuse blow? Report back here.
10. Remove the ignition key.
11. Re-connect the fuel pump assembly's five wire connector.
12. Remove the jumper on pins 3 & 5 of the Circuit Opening Relay & re-install this relay.
 

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Discussion Starter · #3 ·
Yeah I look at these while diagnosing the issue and did these tests.
First test doesn't blow the fuse.
Second test did. Would I still do test 3 even if second test one blew the fuse?
I have also disconnected the fuel pump and the still blew so I don't think that is the issue.
 

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Second test did [blow the EFI fuse]. Would I still do test 3 even if second test one blew the fuse
Given the results of Test 1 and Test 2, for now, there is no need to do Test 3. I trust you were super careful with these tests and did exactly as described.

Does the EFI fuse blow every time you do Test 2?

I would next check for grounds between terminal 3 of the EFI Relay and terminal 3 of the Circuit Opening Relay.

A bad relay is also a possibility.

I will edit this post and add a bit more in a little while. Please check back.

Edit 1: See attachment. What is outlined in green is what I would next explore for grounds.

Test 4
1. Remove the Circuit Opening Relay.
2. Disconnect the Idle Air Control Valve connector.
3. Disconnect all three VSVs shown in the diagram. (I have to hunt for where one of these is. Will post back.)
4. In the engine bay, disconnect data link connector 1 (DLC 1).
4. Turn the ignition key to the "On" position (engine off).
5. Does the EFI fuse blow? Report back here.
6. Remove the ignition key.

I have to study for how to make these disconnections. Maybe you will figure this out before I do. You could also do some ground checks, but I think I would want to see the fuse blow for some assurance in my diagnosing.
 

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-- For the three VSV connectors and the IAC valve connector, see pdf page 28 of 1996Rav4EWD.pdf. The only connector that may be hard to reach is the VSV (EGR). It is behind the engine block. On a FWD Rav, it is pretty easy to reach. On a 4WD Rav, it is hard to reach. Here is a great photo of its location:
151688

The photo is a view while lying on the ground, with one's head under the engine, feet pointing to the front of the Rav4, looking up. Thanks to Sed1999Rav4 for the photo.

-- Page 27 of 1996Rav4EWD.pdf shows Data Link Connector 1 (DLC 1). I think the wire at terminal 12 of DLC 1 is hard-wired. Instead of disconnecting DLC1 for Test 4, you might leave DLC1 connected for now.

-- At some point you may have to unfasten connector IG1, as shown in green on GroundCheck-1.pdf. The physical location of IG1 is shown on pdf page 37 of 1996Rav4EWD.pdf . Detail of the female and male sides of the connector is shown on pdf page 38 of 1996Rav4EWD.pdf.
 

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Discussion Starter · #7 ·
Yeap that was my next test. I disconnected the VSV, idle air and the rest of those sensors. Still popped. I couldn't find anything to disconnect for the DataLink Connector. The only fix was disconnecting the ECM C connector. Then it started right back up like nothing happened lol.
 

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Yeap that was my next test. I disconnected the VSV, idle air and the rest of those sensors. Still popped. I couldn't find anything to disconnect for the DataLink Connector. The only fix was disconnecting the ECM C connector. Then it started right back up like nothing happened lol.
-- Did you disconnect the IG1 connector? Or is that what you mean when you say "that was my next test"?

-- For the next check, I would next disconnect both the negative and positive terminals of the battery. I would disconnect the ECM's C connector. On the harness side of the C connector, with a multimeter, I would test each pin for continuity to a clean ground point on the Rav4. Any grounds?
 
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