TheDurk
Elite Member
Great work! Hopefully someday this knowledge gained will help you out on your own car or in your work. I know it's happened to me where things I've learned helping folks has come in handy later.
all that for nothing
- Thread starter Wayne
- Start date
Great work! Hopefully someday this knowledge gained will help you out on your own car or in your work. I know it's happened to me where things I've learned helping folks has come in handy later.
Oh.
I was going to update the thread but see that Kyle has done that already. The vehicle is still running good as new, I'm happy to report! Kyle is da man! And I'm pretty dangerous with a multitester now.
I still have to test the rest of the ECM grounds to find out what went wrong but I'm kind busy on other things. I will update when I get around to that. I've driven a couple hundred miles w/no issues and after all that fun dropping the tank I'm gonna take a break from car repairs. But I will finish the job.
I was going to update the thread but see that Kyle has done that already. The vehicle is still running good as new, I'm happy to report! Kyle is da man! And I'm pretty dangerous with a multitester now.
I still have to test the rest of the ECM grounds to find out what went wrong but I'm kind busy on other things. I will update when I get around to that. I've driven a couple hundred miles w/no issues and after all that fun dropping the tank I'm gonna take a break from car repairs. But I will finish the job.
Last edited:
Ok, I know this thread is 9 years old, but I’m having very similar issues as Wayne, and I’m in need of some help. ‘97 4Runner base model, stock, 3rz 5-speed 2wd non-california.
I got stranded on the side of the highway the other day. Suddenly losing power and misfiring and couldn’t keep my speed up. Pulled over and the engine was still running, but super rough. Got towed home and started doing some basic diagnostics. Here’s where I’ve gotten so far.
At home, I couldn’t get it started at all. Only two codes for the check engine light: p0420 and p0402, but I’ve driven it with those two codes for years. I was suspecting a fuel starvation issue. Checked the EFI relay by listening and feeling for a click when I had my girlfriend turn the key to on, it’s all good.
Then went to check the circuit opening relay. No click when I turned the key to on. I got my multimeter out and read 12.4V at both white/light blue wires going to the relay. BUT tested the green/yellow wire, and no ground (or at least a very bad ground). It was reading 2800 ohms from the green/yellow wire to the chassis. I back-probed the green/yellow wire at the circuit opening relay and grounded it with my own wire to the chassis. Turned the key to on, and click from the relay. So the relay works.
Then I checked the continuity across the green/yellow wire from the relay to the ecm. No resistance, all good.
Then I wanted to check all the ecm’s ground(s). I wasn’t exactly sure which grounds to check, so I checked as many as I knew. Checked the ground on the intake manifold, which I believe the ecm grounds to. Checked the one on the head below the coil packs, the ones in the engine bay inside the left fender, the one from the valve cover to the firewall, the two in the left kick panel. That’s all I could find. They all seemed fine. Wasn’t sure where to go from there. Why isn’t the ecm grounding the green/yellow wire??
So I went back to the circuit opening relay, and grounded the green/yellow wire to the chassis again. Turned the key to on, felt the click again. Went under the back seat and uncovered the wire connector to the fuel pump. Unplugged it and read 12.3V at the light blue/orange wire. Checked the white/black wire and it was grounded. Plugged the connector back in, but I didn’t hear the pump running.
So now I’m baffled. There seems to the two issues (or three issues if you include my amateur understanding of all of this). One, the green/yellow wire at the circuit opening relay is not grounded, and two, the fuel pump seems to be not working? Someone help me out here. Am I missing something? Having both of these problems at the same time seems possible, but an unlikely coincidence. Both would seem to make the car not run/start, but they happened at the same time?
I don’t really want to just throw parts at it like a new fuel pump or another ecm…
I got stranded on the side of the highway the other day. Suddenly losing power and misfiring and couldn’t keep my speed up. Pulled over and the engine was still running, but super rough. Got towed home and started doing some basic diagnostics. Here’s where I’ve gotten so far.
At home, I couldn’t get it started at all. Only two codes for the check engine light: p0420 and p0402, but I’ve driven it with those two codes for years. I was suspecting a fuel starvation issue. Checked the EFI relay by listening and feeling for a click when I had my girlfriend turn the key to on, it’s all good.
Then went to check the circuit opening relay. No click when I turned the key to on. I got my multimeter out and read 12.4V at both white/light blue wires going to the relay. BUT tested the green/yellow wire, and no ground (or at least a very bad ground). It was reading 2800 ohms from the green/yellow wire to the chassis. I back-probed the green/yellow wire at the circuit opening relay and grounded it with my own wire to the chassis. Turned the key to on, and click from the relay. So the relay works.
Then I checked the continuity across the green/yellow wire from the relay to the ecm. No resistance, all good.
Then I wanted to check all the ecm’s ground(s). I wasn’t exactly sure which grounds to check, so I checked as many as I knew. Checked the ground on the intake manifold, which I believe the ecm grounds to. Checked the one on the head below the coil packs, the ones in the engine bay inside the left fender, the one from the valve cover to the firewall, the two in the left kick panel. That’s all I could find. They all seemed fine. Wasn’t sure where to go from there. Why isn’t the ecm grounding the green/yellow wire??
So I went back to the circuit opening relay, and grounded the green/yellow wire to the chassis again. Turned the key to on, felt the click again. Went under the back seat and uncovered the wire connector to the fuel pump. Unplugged it and read 12.3V at the light blue/orange wire. Checked the white/black wire and it was grounded. Plugged the connector back in, but I didn’t hear the pump running.
So now I’m baffled. There seems to the two issues (or three issues if you include my amateur understanding of all of this). One, the green/yellow wire at the circuit opening relay is not grounded, and two, the fuel pump seems to be not working? Someone help me out here. Am I missing something? Having both of these problems at the same time seems possible, but an unlikely coincidence. Both would seem to make the car not run/start, but they happened at the same time?
I don’t really want to just throw parts at it like a new fuel pump or another ecm…
Update: I figured it out
Went back to double check all my findings that I listed above, and I thought of something that i hadn’t considered before. I decided to check the ground from the circuit opening while cranking the starter. Previously, I had only checked the ground with key out and with key to on. Hey, what do ya know, the ecm grounds the relay when your cranking the engine! I guess the ecm commands the fuel pump to run (via the ground at the circuit opening relay) only when the engine is turning, i.e. when cranking or when running.
Ok, so there’s no issue with any wiring or with the ecm since I’m getting power to the fuel pump and the fuel pump is grounded. Then, I thought of another thing I hadn’t done before: I checked the resistance of the fuel pump. Thousands of ohms. The fuel pump is definitely the issue. Went out and bought a new denso pump and strainer. Four hours of dropping the fuel tank, replacing the fuel pump, and wrestling to get the fuel tank back in with a lot of swearing, and voila, the truck fires right up.
To put my findings briefly for anyone who’s interested: the ecm commands the fuel pump to run by actuating the ground at the circuit opening relay when the engine is turning. Correct me if I’m wrong! I’m just some schmuck trying to keep my 4Runner alive as long as possible and learning as I go.
Went back to double check all my findings that I listed above, and I thought of something that i hadn’t considered before. I decided to check the ground from the circuit opening while cranking the starter. Previously, I had only checked the ground with key out and with key to on. Hey, what do ya know, the ecm grounds the relay when your cranking the engine! I guess the ecm commands the fuel pump to run (via the ground at the circuit opening relay) only when the engine is turning, i.e. when cranking or when running.
Ok, so there’s no issue with any wiring or with the ecm since I’m getting power to the fuel pump and the fuel pump is grounded. Then, I thought of another thing I hadn’t done before: I checked the resistance of the fuel pump. Thousands of ohms. The fuel pump is definitely the issue. Went out and bought a new denso pump and strainer. Four hours of dropping the fuel tank, replacing the fuel pump, and wrestling to get the fuel tank back in with a lot of swearing, and voila, the truck fires right up.
To put my findings briefly for anyone who’s interested: the ecm commands the fuel pump to run by actuating the ground at the circuit opening relay when the engine is turning. Correct me if I’m wrong! I’m just some schmuck trying to keep my 4Runner alive as long as possible and learning as I go.
jgue467
Senior Member
That is standard for 3rd gens.
19963.4lsr5
New member
How did the gasket surface of the tank look? That’s a known place to rust and cause EVAP codes.
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