02 LW300 V6 Fuel Pump and OBD2 Trouble

[LUXWAG]

Hello, here’s what is going on. 2002 Saturn Luxury Wagon 300 V6 with 113,000 miles has been a very reliable car until now!

What happened?
Turn the key to start, engine turns over and it doesn’t fire up.
I cannot hear the fuel pump prime when turning key to run
Service Engine Soon and Service Wrench light on.

What I did?
I plugged my OBD2 reader into the port and pulled the following codes
-P0201
-P0202
-P0203
-P0204
-P0205
-P0206
(All of those refer to Injector circuit malfunction)
-P0056
(Oxygen sensor heater control circuit, low voltage)

I then cleared all codes and the damn thing fired right up.
I turned off and started the car back up three more times and then went inside thinking it was somehow fixed.

What Happened Next!?

2 hours later i went outside to start the car and the motor turns over and doesn’t start. I turn the key to run and I can’t hear the fuel pump prime. The same service engine soon and service wrench light come on.
And this time the fuel gauge shows empty even though it has a full tank of gas.
So I hooked up my OBD2 reader and now the reader won’t link.

I’ve checked fuses and swapped relays. Charged the battery and I can’t start the car or pull the codes. My code reader works on my other vehicle and every time I hook it up to this car it starts to load but it can’t link up to the vehicle.

I’m guessing it’s a ECM problem.

What do you think?

[fdryer]

Readers do not communicate directly to the engine computer. GMs body control module (BCM) communicates directly to readers/scantools from the OBD II port. The bcm communicates to every module either serially or thru canbus then passes info thru the OBD II port. The gas gauge is driven by the bcm. A blown fuse may be the reason for not connecting to the OBD II port (12v on pin 16). This may be the beginnings of a faulty bcm since it's the gateway for every module thru the OBD II port for determining error codes, programming, diagnostics, etc. Did you check the two inside foot wells for blown fuses too?
The ecm provides the 2-3 second fuel pump signal at ignition on time when the engine isn't started. Depressing the fuel test port for a spray of fuel is one way to check fuel pump operation without a fuel pressure gauge. When the engine's cranking, the ecm turns on the fuel pump from crank sensor timing signals.

How's the main power system - battery, battery cables, their connections? Free of corrosion, snug connections. Battery age? Tested (free) at AutoZone or other stores offering free battery/alternator testing?

[LUXWAG]

Thank you fdryer for the quick response!

I had the battery tested and it was bad. The battery was 5 years old so that was to be expected. I bought a new battery and installed it hoping that was the problem but nothing has changed. No start and the fuel gauge is still on E and the service lights are both on and the OBD2 reader won’t link. I think tomorrow I will check the battery cables and the two interior fuse blocks.

I changed the fuel pump last summer using the “cutting a hole under the backseat” method so I’m fairly confident in the fuel pump working but maybe I’ll try to find that fuel pressure gauge I had laying around and test it out.

[fdryer]

If you have AutoZone nearby, they should have loaner tools like a fuel pressure gauge.

One fuse powers injectors. As a rule, ecm failures are rare but bcm failures do occur according to past history here. If your descriptions are accurate, the bcm may be hinting of impending failure.

The ecm runs the entire EFI system to manage the engine and emissions control. The bcm runs almost everything else except the air bag system and abs/tc. Those have their own independent modules. The bcm drives all interior/exterior lighting, gauges, indicators, manages GMs anti theft system - Passlock, exchanging a password after checking for ignition switch rotation, sending a go or no go signal to the ecm to enable or disable injector operation. In a no go situation, the security indicator flashes quickly - the starter will crank but the engine will never fire up. Normal starting in with the security indicator off. The bcm is the gateway for all error codes from every module.

One way to test for either loss of spark or fuel would be spraying starting fluid into the throttle body. If spark occurs, the engine should fire up and point to possible fuel issues. If the engine doesn't startup oon starting fluid then this tends to point to a spark issue.

[LUXWAG]

So I checked the battery cables and they look ok, no corrosion. I removed the ground to the body and cleaned it up and reinstalled. I checked every single fuse under hood and in the side kick panels. All fuses were good. I had my wife try to start the car as I checked the fuel test port and I had no pressure from the port. We tried several times.

Also after turning ignition to RUN the airbag light comes on and stays on. I don’t know if this is normal.

The OBD 2 still won’t link up.

Also, if the ignition is in RUN I have voltage to the purple wire that goes to the connector on top of the fuel pump. I’m not sure what that goes to, if it’s the pump or the sending unit?

I wonder if I have a bad fuel pump among other problems?

[LUXWAG]

Ok, so I spayed starting fluid into the throttle body and the car started for a couple seconds. Now I’m thinking this is a fuel issue. My first thought is to replace the fuel pump but because the OBD2 reader tool still won’t link up, this may be more of an electrical problem.

[LUXWAG]

New development…

I tried starting the car again and this time the engine cranks no start (I did not spray starting fluid in throttle body this time) but the fuel gauge now works and the service wrench light does not appear but the reduced power light comes on.

I plugged my obd2 reader into the car and it links up!

Here are the codes…
P0261,P0264,P0267,P0270 (Injector control circuit low voltage)
P0444 (evap emission system purge control valve circuit open)
P0037(oxygen sensor heater control circuit high voltage)
P0057(oxygen sensor heater control circuit low voltage)
P1516(Manufacturer control)
U2105(Manufacturer control) (Transmission code)


What the hell is going on? This has to be an electrical problem coming from the bcm or ecm?

[Rj 2000 LS2]

Have you considered the fuel filter is plugged? Disconnecting the fuel filter and testing for fuel pump is working might be good to isolated the a fuel delivery issue.

[fdryer]

The fuel pump runs for 2-3 seconds when ignition is turned on, engine not started. A fuel pressure test is done at this time without starting the engine. With the engine running, fuel pressure should be the same value. After the 2-3 second time out, the power to the pump stops. It's a safety issue, disabling power to the fuel pump if the engine isn't started or running. When starting, the engine turns over when the crank sensor generates timing signals the ecm needs to operate the EFI system. The ecm turns on fuel pump, initiates timing for spark and pulses injectors. If the engine stops for whatever reason with ignition still on, the fuel pump stops running (safety). This info is from service manuals describing fuel pump operation.

For advanced troubleshooting, you can remove the fuel pump relay and read the pinouts on the relay. Carefully jumpering relay socket terminals 30 and 87 will send 12v power to the pump immediately to generate fuel pressure. You may be able to hear a quiet hiss on the fuel rail over the engine and hear the hum of the fuel pump using the butt end of a screwdriver pressed into one ear with the steel tip pressed onto a rear panel, fuel nozzle, whatever.

The erratic bcm operating intermittently may be announcing its demise. Ignore the error codes as they're false positives. For the moment, erasing error codes by disconnecting battery negative for a few seconds may help from distracting you with false errors. The bcm lies on top of the glove box.

[LUXWAG]

I went to a junkyard and searched for a Lw300, hoping to find a used BCM, but there were none. Not surprised, these Saturns are becoming harder to find. I called the local GM dealer service department and they said they could program a new BCM for $190. I decided to order a new BCM from RockAuto for $250 and give it a shot.

If I jumpered the fuel pump relay and the fuel pump does turn on, what does that mean? Obviously the fuel pump works, but does that point towards the BCM going bad or the ECM going bad?

I must admit that I’m very confident working on anything mechanical but my weak point is electronics and fuel injection.

[Rj 2000 LS2]

Everyone will poo poo on this idea, but it is inexpensive and easy to try. Nobody believes this, but it is true. If the ECT sensor is faulty and reporting a high temperature... the injectors will be shut off. It is for safety to not pure fuel on an engine fire. Change the ECT.

I would not worry about all those codes until you get the engine running. Then, clear the codes and start fresh. O2 sensor codes don't necessarily mean the O2 sensors are bad.

[fdryer]

Originally Posted by LUXWAG

Ok, so I spayed starting fluid into the throttle body and the car started for a couple seconds. Now I’m thinking this is a fuel issue. My first thought is to replace the fuel pump but because the OBD2 reader tool still won’t link up, this may be more of an electrical problem.

You're describing a possibility of two problems. The suggestion to jumper fuel pump relay socket terminals 30 and 87 to power the fuel pump immediately and try starting accomplishes two things; 1)either the fuel pump runs or not, and 2)if it runs will the engine startup up and stay running? Security must be OFF, not flashing during starting. This assumes the ecm is fine whether or not the bcm is acting up and interfering with the ecm operating the EFI system.

The BCMs role to prevent the ecm from operating as part of Passlock anti theft operation if it sends a fuel password to the ecm to allow injector operation. Operating injectors is an ecm function. Running the fuel pump is also an ecm function. At least once during troubleshooting you were able to get the engine running briefly when spraying starting fluid to verify the ecm is operating. Whether the fuel pump is acting intermittently or failed outright requires testing by jumpering fuel pump relay terminals in the fuse box. The pump must run to supply fuel and pressure to the EFI system. Spraying starting fluid and getting the engine to run briefly seems to point to a fuel pump issue in addition to possible bcm failure. I think you're dealing with multiple issues.

[LUXWAG]

Is it possible that the fuel pump going bad could cause the BCM to act erratically? I’m going to try jumpering the fuel pump relay tonight and see if that does anything.

[fdryer]

No, fuel pump operation and circuit is completely separate from bcm circuitry.

[LUXWAG]

Here’s where I’m at now…

I disconnected the battery and removed the BCM on Sunday 2/20/22. Then today I decided to try the fuel relay jumping test.

When I installed the BCM and reconnected the battery, the service wrench light and service engine soon light came on. Engine turns over but no start. Also the gas gauge says Empty. Then I tried starting again and engine turns over no start but this time the service wrench light turned off and the gas gauge works.

Then I tried to start again and engine turns over no start and service wrench light, service engine soon come on and fuel gauge shows empty. My OBD2 reader won’t link.

Then I jumped terminals 30 and 87 on fuel pump relay and I had fuel pressure and could clearly hear the pump running. I tried to start but engine turns over, no start. Same lights on dash and fuel gauge on empty.

So I know the fuel pump works.

I think this is the BCM causing the problem.?

[Rj 2000 LS2]

Disconnect the ECT sensor and start your engine!

[LUXWAG]

Tried disconnecting ECT sensor and nothing changed.

[fdryer]

1- is security OFF? Passlock security is a yellow car symbol with an oversize padlock. When its flashing, the ecm disables injector operation while starting. Security must be OFF during starting.

2- hearing the fuel pump, did you depress the fuel test port to verify fuel spraying out. On the engine are two stainless fuel lines towards the rear of the engine. One has a black plastic cap covering the fuel test valve. Remove the cap to see the Schrader valve, the same valve on every tire but seals are fuel resistant. Cover loosely with a rag with pump running and fuel should spray out under pressure (anywhere between 39-49 psi when measuring with a fuel pressure gauge). Verifying fuel spraying out implies the fuel rail is pressurized to feed injectors when the ecm commands them to cycle when starting and running. Be sure fuel pressure sprays fuel.

3- spark is difficult to test but can be tested indirectly by spraying starting fluid into the throttle body before starting. Guaranteeing fuel into the intake air system leaves spark in question when starting up. If the engine doesn't startup then it's presumed there's an ignition problem. The front three cylinders have an ignition coil pack. The rear three cylinders have an ignition coil pack. Both coil packs are controlled by the ecm.

The bcm does not control the EFI system. The ecm (engine control module) runs the EFI system. The only way the bcm can prevent the engine from running is if Passlock security flashes during starting, sending a signal to the ecm to disable injector operation. With security off, the bcm has no role in engine running. Flashing security indicator is the anti theft program being enabled and actively disabling the engine from starting and running. As long as security is off, you're troubleshooting the EFI system.

The bcm runs security, all lighting, gauge dials/indicators and gathers error codes from modules then passes codes thru the OBD II port to a reader or scantool.

[02LW300]

Hey guys, this is LUXWAG. I was unable to post so I made a new username.

So here’s where I’m at today

-engine turns over, no start, service wrench light and service engine soon light, fuel gauge shows Empty, OBD2 scanner won’t link
-jumping fuel pump relay makes fuel pump work and I get 41 PSI fuel pressure at fuel rail test port but still doesn’t start/run
-spraying starting fluid in throttle body does not get car to start/run.
-battery is new and fully charged
-tried starting with ECT disconnected and doesn’t start/run
-security is off and doesn’t blink when starting

So I know
-Fuel pump works but only when bypassing relay
-not getting spark or fuel on startup
-OBD2 port won’t link to reader


Any ideas here? Are there any sensors going bad that would cause these symptoms? It’s like the ECM is preventing the ignition cycle?

[02 LW300]

Good name, I will just hang out at the Saturn forum from now on.
Andy