02 L100 - Fuel pump relay.

[xhawkx]

I have a 2002 L100 that won't start.
I had determined that I wasn't getting any fuel pressure at the fuel rail, so I replaced the fuel pump. The car ran great for 1 day, then stopped again.

I jumped the fuel pump relay and the pump would run and the car would run.

Swapped out relay with winshield wiper relay. . (same part #) No go.

I tested for power to the coil of the relay from the ECM when the key 1st gets turned on. No power. Checked for power while cranking. No power.
I do have ground at the other side of the coil.

I checked continuity from the positive side of the coil in the fuse box to the ECM connector (Drk grn wire/white stripe), I have 1.0 ohm resistance.

Is this a bad ECM? or is there something else that would cause the ECM to not energize the fuel pump relay?
Just want to eliminate any other possible causes before ordering a replacement ECM.

P.S. No codes in the ECM. battery, oil and brake light on dash. nothing else.
disco'd positive side of battery cable and grounded for 20 min. Retested no change.

Thanks

[fdryer]

Are you sure you tested terminal 86 for 12v? Its there only for 2 seconds at ignition ON and goes away. Starting should show 12v as long as the engine is cranking or running.

[xhawkx]

yes..
30 has constant 12v (positive side of contact)
85 has a good ground (1.0 ohm to ground) (negative side of coil)
86 never gets voltage. I hooked up the meter and placed it on the windshield while I sat in the car and turned on the ignition... nothing.. started cranking... nothing..

I then had a buddy come over.. and I held the meter on 86 and ground.. had him turn on ignition and turn over. No power at all.

If I jump 30 and 87 fuel pump runs.

[fdryer]

Ok, here's another wiring diagram you can use. Trace and check continuity to the dark green wire from the pcm's J1-46 (pin) to the pump relay terminal 86.

[xhawkx]

Originally Posted by xhawkx

I have a 2002 L100 that won't start.

I checked continuity from the positive side of the coil in the fuse box to the ECM connector (Drk grn wire/white stripe), I have 1.0 ohm resistance.

Thanks

I think I covered that in the original post..

[fdryer]

Oh! A sedentary brain cell sometimes falls asleep.

Tried to measure for the 2 second 12v signal coming from the pcm? This may take two people to coordinate efforts. And to complicate things, you can't cycle the ignition switch as quickly; at least 15 seconds is needed between ignition ON cycles otherwise another timer prevents pump cycling................ Wait a full minute between ignition ON cycles. A test light can be used also if you want a visual indicator instead of using a meter.

[xhawkx]

Thank you for your assistance in providing tips for troubleshooting.
I did meter it with a friend. Had him turn the ignition on while I held the meter to the ECM wire. No voltage.

Is there anything else that might cause the ECM to not emit 12 volts to the pump relay for the 2 seconds on ignition on?

(Security light is not on on the dash, so I don't think it is the security feature engaging.)

[fdryer]

Security has no role in disabling fuel pump operation. What may work is removing power to the pcm entirely, PCM fuse disconnect or battery negative to force a reset. There has never been a reported pcm failure, losing this signal, killing pump operation so I'm inclined to believe something is preventing the pcm from cycling this signal. Removing all power to let this pcm default back to presets may help. It can't hurt at this point before contemplating replacement.

Are there any aftermarket mods that may cause this circuit to stop operating? If I were in your shoes I would disconnect this wire at the pcm connection (cut it if necessary as you can always splice in new wire) to ensure the wire isn't grounded somewhere and test for a 12v signal again at the pcm.

[xhawkx]

Originally Posted by xhawkx

P.S. No codes in the ECM. battery, oil and brake light on dash. nothing else.
disco'd positive side of battery cable and grounded for 20 min. Retested no change.

^^ From my original post.^^

(I figured hooking positive battery cable to ground for 20 min would be enough to reset the ECM).

Good thinking on checking for a possible ground short on that line.. I will do that tomorrow. and if necessary cut the wire and check for 12 volts coming directly out of the ECM.

No mods have been performed on this vehicle.

[xhawkx]

Ok. Finally had a decent day weather wise to perform the next steps.
I did not read an short to ground on the wire from the ECM to the fuel relay. I cut the fuel relay wire, and tested right at the ECM. No signal from ECM to the relay wire when the ignition is first turned on. (within 2 seconds).

[fdryer]

This is getting intense. I dislike asking anyone to do something I wouldn't do but this failure to see 12v to power the pump relay now needs to checked right at the pcm. The pcm connector will have to be disconnected (disconnect battery negative temporarily) to examine the male/female terminals and continuity from the connector terminal to the cut wire and to the relay terminal to ensure complete continuity before concluding pcm failure. If you can, tug the wire in question to test its mechanical connection - that it doesn't pull out easily. If you are sure of complete wire continuity from pcm to relay terminal, try measuring for voltage again at the pcm. Measure relay ground for 12v if the wiring diagrams are wrong.

If you want, pm an email address and I'll send background info about Passlock security and wiring diagrams as well as how the EFI system works with security. It won't hurt to start searching for used pcm's..........

[xhawkx]

Sorry for the long delay.
This is my daughters car and she had to save up for some parts.
I just installed a replacement ECM and now the fuel pump relay does turn on. the ECM was definitly the problem there.
I currently am getting a flashing security light, so it won't start. I am performing the following steps to attempt to reset it
Turning key to on for 10 min waiting for flashing light to stop.
repeat 3 times.

Is this correct?

[fdryer]

Since you pm'd and successfully fixed this problem with a replacement ecm, it appears that as our Saturns age, ecm's may fail too. Thank you for following up to close this thread.

[xhawkx]

Security reset... Car starts just fine now except for a vacuum leak I need to track down.

[xhawkx]

ARG.. I am at a loss now. Car was running just fine after ECM replacement for 1 day. NOW back to old problem again.
Turn key on, fuel pump relay does not engage.
Car won't start. Fuel pump relay won't engage when turning over.
Jump relay contacts to pump relay and it starts.
Swapped out relay and still no start.
Seems once again I am not getting a signal from the ECM to the fuel pump relay.
Any ideas what else might cause the ECM to not turn on the pump relay?

[fdryer]

Well, this is abnormal. Use wiring diagrams from Posts #2 and #4; a parallel wired small 12v test light can be wired temporarily to pump relay terminal 86, the 12v command signal from the ecm to power the relay. Two lengths of wire, (no more than 18 gauge) one inserted into terminal 86 with the relay holding this wire in place and the other end run into the car. This end connects to either a 12v test light or spare 12v bulb with a small length of ground wire attached anywhere to the car chassis. This light should turn on; when the ign switch is first turned on (engine off) and stay on for 2 seconds then turn off OR when starting/running and stay on as long as the engine's running. All you're doing is wiring a visual indicator to let you see the ecm command signal turning on the fuel pump relay. A 12v LED will work too but you'll have to pay attention to polarity if insulation isn't color coded - test wiring to the car battery will tell you which wire is positive and negative when it won't light up by reversing leads.

This test light can help determine if the command signal is intermittent, indicating a possible wiring break making intermittent connection/disconnection.

Total car mileage? Worn out fuel pump?

[xhawkx]

168k miles.
When the problem 1st showed itself, I assumed it was the fuel pump, so I replaced it with a brand new one. The car worked for one day, then this problem.

I pulled the replacement ECM and noticed some condensation on the bottom. I left it out and put the old back in. No run.
I came in and posted my message above and relaxed for a bit.
I just went out and put the replacement ECM back in, and hooked up a multi-meter as you indicated (instead of a bulb). The ECM turned the pump on, and the car fired up. However the MM wasn't showing a reading. Seems that the postivie voltage isn't on 86 but on 85. Wired it that way and saw the voltage and the car ran.

While running, I grabbed a hold of the wiring harness, and wiggled it all the way from the ECM to the fuse/relay box. Car kept running.

I really don't think it is a wiring harness issue, since I had already metered that wire from the relay to the ECM when the car would not run.

Wondering if there is something else on the vehicle that might tell the ECM not to turn on the fuel pump either when key 1st turned to on, or when the crank position sensor is detecting rotation.

Thoughts?

[fdryer]

Ok, terminal 85 is the command signal (12v) from the ecm instead of 86. My bad and great heads up on your part to find my error. I think you should wire the light in parallel anyway as a way to see a visible indicator as described. The only other possibility may be the ground wiring for the relay coil.

There's only one command signal and its on terminal 85. The ecm does not prevent the pump signal from operating for any reason and wiring the light will show you on every ign ON cycle or engine running cycle.

You already demonstrated two ecm's working exactly the same way. I believe its either the wire or termination (ecm or relay side) that's intermittent.

By using the test light you're eliminating the need to use a voltmeter. You're at the very advanced level of electrical troubleshooting. Not electronics.

Is there any aftermarket or home made alarm system that disables pump operation?

Please update your profile to reflect the car year and engine size under your name. I can't send pm info without it.

[xhawkx]

Profile updated:
2002 Saturn L100 2.2L

[xhawkx]

No after market or home made alarms