I have a 2001 Cadillac Seville SLS that has been having Intermittent starting problems. Presently the vehicle will not build-up fuel pressure in order to start to 41-47 psi unless I remove the rear fuse/relay box IGN 1 micro relay. With this relay removed, I can hear the fuel pump build-up the required psi and then I confirm the build-up of that psi by looking at my test fuel psi guage under the hood, the car then starts no problem, and runs no problem with relay not installed. Whenever I re-install this micro relay the fuel sys will not build-up the required psi, it just stays at 0 psi, and of course it will not start. I just replaced the fuel pump sending unit assy plus fuel filter today.

What is in the wiring diagram that can cause this problem??? Tried swapping micro relay with other positions and still same problem which confirms the relay is not bad.

 

The IGN 1 relay activates power to three fuses. They are: VENT SOL 10 A fuse to the evaporative emissions canister vent solenoid, SIR 15 A fuse to the inflatable restraint sensing and diagnostic module, and IGN 1 10 A fuse.

Please focus in on the problem by removing each of the fuses to see which circuit has the problem.

 

It will also help diagnose the problem if you provide a list of the current trouble codes from your dashboard. With the ignition on but not running, press and hold the two outside driver info buttons to see them.

 

Thanks for your response. I removed fuses one at a time @ rear BEC. Positions 8, 11, 12 with no help to start problem. I also removed the IGN 1 @ front BEC and isolated the two, no help either. I can hear Alot of clicking at the rear BEC?

To top it off, this morning while driving to work I was doing 55 MPH and car just suddently quit, dash went black.....It felt like the PCM under the hood quit, because I heard a noise along with the sudden stopping of engine. When I pulled over, I had to remove the IGN 1 relay @ rear BEC to start the car again, I decided to drive to work without it installed. ??????????

 

When I shut off the car, and turn ignition ON, with IGN 1 relay installed, all I get from dashboard is a frozen screen displaying SERVICE AIR BAG and RED Icon in lwr rh corner stating AIR BAG. When I hold the INFO buttons together I get nothing...screen frozen on that message???

 

The screen is probably frozen on the air bag message, but just to make sure here are more detailed instructions to activate the codes:

The ignition on.
Press and hold: INFO UP and ON/OFF at the same time for a few seconds.
The dash should say: ALL?
Press: ON/OFF
The dash should say: ALL CODES?
Press: ON/OFF
The dash should slowly scroll thru the codes and say: ALL CLEAR CODES?

 

Removing all three fuses at the same time should repeat the condition caused by removing the IGN 1 relay under the seat. Please test by removing all three fuses simultaneously and try to start the vehicle. If that works try again including all combinations of only two removed. If that works double check with just one of the fuses removed. This relay is controlled directly by the ignition switch not by the PCM.

My guess is that the problem with the fuel pump is related to one of the fuel metering modes of operation. My first thought is that an ignition or ignition-wiring problem is causing the PCM to shut down the pump. If you are able to start the car by removing the relay and the car will continue to run after the relay has been installed then the problem may be with the starting mode. During the starting mode, with the ignition on, the PCM is supposed to energize the fuel pump relay for 2 seconds to build up fuel pressure. It could be that the ignition is bad or that there is a short or break in a wire between the ignition and the PCM or IGN 1 relay. See Third and Fourth below.

The problem could also be with the fuel cutoff mode. The PCM enters this mode when one or more of the following conditions are met:
Ignition off.
Ignition on but no ignition reference signal.
Engine speed too high.
Closed throttle during high speed.
Extended deceleration.


The problem is most likely caused by a bad electrical component such as a switch or sensor or by a short or break in the electrical wiring, but it could also be caused by a bad PCM. Test the electrical components and wiring first because they are the more likely culprit and will cost less to fix.

First: In order to narrow down the possibilities, take your car to Schuck’s or someplace where you can borrow a scan tool and get the codes. Also get the freeze frame data from when the fuel pump first failed.

Second: Check the fuses. Check all of the fuses in both the underhood and rear fuse boxes. Especially check the PCM IGN fuse underhood because it tells the PCM that the ignition is on.

Third: Pull the IGN 1 relay and check the conductors in the fuse block. Remove the relay and use a voltage meter or test light to determine that L2 is always hot. You can make a test wire that fits in the slot by hammering a piece of copper house wire flat. Remove the fuses and relay and use an ohmmeter to test J3 for conductivity to the three fuses. Test J2 for power when the ignition is on and in start and no power otherwise. Test L3 for a good ground.

Fourth: Check the ignition switch and wiring to make sure they are not confusing the PCM. Use a voltage meter or test light to check for power at connector C1 pin 63 and at pin 19 for voltage when the ignition is on and in start and no voltage in the off position. Pin 19 should also have voltage in accessory, but that doesn’t matter to us here. Check C1 pin 6 for voltage in start and no voltage in the other positions. (C1 is the back connector to the PCM. The PCM is located in front of the air filter. Open the air filter cover with a T30 star screwdriver and remove the two covers that come off when the screw is loosened to expose the PCM. If you see the air filter you are in the wrong place. The PCM is toward the front and you don’t have to loosen the clips to see it. Remove the bolt to C1 with a 7mm socket.)

Fifth: If that didn’t work, report back on the codes and your results with the tests and I will try again.

A word of advice gained from experience --- Don’t start changing a bunch of good parts until you isolate and identify the problem. Use an ohmmeter and voltage tester instead.

I saw your other post where you had a P0449 code, which indicates that the commanded state of the evaporative emission canister vent valve does not match the actual state of the valve. However since the IGN 1 relay provides power to the EVAP solenoid and since this problem surfaced after the fuel pump problem, it is likely that the P0499 code was triggered by removing the IGN 1 relay. The problem will probably be cured when you fix the main problem.

The IGN 1 relay also provides power to the airbag system, so removing the relay probably caused the warning messages. Incidentally your airbag system won’t work with the relay removed. You should also be careful in case the system accidentally inflates when you reactivate the system. (The manual instructs us to stand clear of the airbag the first time we turn on the ignition after restoring power to the system.) This problem will probably be cured when you fix the main problem. It is possible that the SIR system

Off topic - If you have a spare fuel level sensor left over from your earlier repair attempt, I would make good use of it.

 

A bad ground might also be causing your problem.

Check for conductivity and clean if necessary:
G301 under the left passenger seat near the rear fuse block.
G104 the front one under the hood on the right.
G201 under the dash.

 

Thanks once again for the quick response also the in-depth information.

Real quick, I started the car like I have been this morning by removing the IGN 1 relay (rear BEC). After driving a few miles, I decided to pull over, and re-install the IGN 1 relay, because I lose the odometer, tachometer, speedometer, cruise control, turn signals and have a constant displayed message of "service air bag" on the screen with IGN 1 relay not installed. Also the engine quit running again at a lower speed today, while I was driving to an ATM. I pulled the IGN 1 relay(rear BEC), re-started car and drove to work with it removed.

So far I've only tried "again" the recommended "fuse" troubleshooting. With IGN1 relay installed and all 3 fuses removed, I do not hear the fuel pump operating which pressurizes the fuel manifold. With all 3 removed and the removal of IGN1 relay the fuel pump operates and the car starts normally. I still continued T/S by re-installing IGN 1 relay and putting in a combination of the fuses back in place and no help. I never hear the fuel pump energize, T/S with these fuses, unless I remove the IGN 1 relay.

I also attempted to turn ignition switch to ON, hold INFO UP and ON/OFF at the same time and the dash does not display "ALL". It continues to repeat "service air bag"

I will try the other tips with an ohmmeter later this evening!

 

The fuse and relay test was helpful because it eliminated the circuits on the switched side of the relay from the problem. When you pull the relay you have broken the circuit on the control side of the relay and allowed the fuel pump to operate. When you pull the fuses with the relay installed you have broken the circuit on the switched side of the relay which did not allow the pump to operate. This makes me think you have a wiring or connector problem on the control circuit, probably on the ground side of the circuit.

Don't bother with testing the PCM connectors yet.

Check both the ground connection and wiring from the underhood IGN-1 Relay and the ACCY relay thru the G104 ground connection. You can do this by removing both the underhood IGN 1 relay and the underhood ACCY relay and use an ohm meter to verify 0 ohms between each relay's control side ground conductor and the engine block. Don't check to the G104 ground screw because you also want to establish that the connection is good.

Check the ground connection and wiring from the rear IGN 1 relay and the F/PMP relay thru the G301 ground connection in a similar manner.

Check the positive control wiring to each of the relays by operating the ignition to run and with all three relays pulled and a voltage tester or test light connected to the proper terminal.

These relays have four conductors. They are always hot at the switched positive, should test the partial resistance of the switched devices, have an ignition switched hot at the control positive, and have a permanent ground at the control negative.