After looking at diagram 642412 Ignition switch schematic I realized I never did check the ignition switch as you recommended earlier. I noticed C2 connector pin E2 IGN 1 relay, I will be checking PCM tomorrow pins 19/63...........

It's been all trail & errror for me, getting familiar with Cadi schematics has been interesting to say the least!

 

Before chasing the ingnition switch, finish checking the G301. The voltage should not have backed up on the IGN1 relay control circuit ground.

Use a voltage drop check not a resistance check. Here is why. It is possible to have a circuit have 0 ohms or no resistance and still have an electrical problem because a conductor or connection in the circuit is too small to handle the load. On a very small wire your ohm-meter will show 0 ohms because it sends a small signal thru the wire to test the conductivity. That same small wire or bad connection with 12 volts behind it could show 5.7 volts because it is able to pass 6.3 volts of the load easily thru it. The other 5.7 volts are backed up, waiting to get thru.

Clean your G301 connection and the other connections in the ground circuit really good and perform another voltage drop check to see if you have fixed the problem.

You can perform voltage drop checks at isolated connections by probing the wires. As a general rule, it is best to have everything connected and the power flowing when performing a voltage drop test.

 

Went thru relay checks again at the rear fuse block, I've learned enough to become dangerous..

Using "FUSE BLOCK - REAR" pg 1of 3 diagram of fuses & relays, it shows the slots with # in it plus horizontal alphabetical listing & vertical #'s.

I removed fuel pump relay # 39 and kept IGN 1 relay installed. F/Pump relay slot C-1 (1540) always shows 12 volts with ignition switch OFF and slot A-1 (465) had 0.3 Volts also.

With meter wire connected to A-1 slot, I turned ignition switch to ON, I then removed IGN 1 relay, and voltage shot up to 11.6V then settled to 10.3V and stayed there.

With fuel pump relay installed and IGN 1 relay removed slot L-2 (1) shows 12 volts continouslyand slot J-2 (3) read 0 volts with ignition switch OFF. With ignition switch ON slot J-2 (3) shot up to 6.0 volts then settled to 4.8 volts.

Fuel pump relay slot C-2 showed 0 ohms (750) along with IGN 1 relay slot L-3 (750). The G301 ground point to rear floor I used for a ground for the meter. It showed little resistance when connected to floor.

If I remember correctly since I didn't write down any notes for this scenario...with fuel pump relay connected and IGN 1 relay removed, ignition switch ON, meter on slot J-2, when the voltage built up to 6.0 V- 4.8V, I heard the fuel pump build up required pressure for start.

Had to go back to the beginning..............???????????

 

I'll keep this simple by writing down my findings.....

Power Distribution Schematic (SIR, VENT SOL, IGN 1 Fuses and IGN 1 Relay) L2 voltage constant 12.58V, J3 Voltage 5.83-6.12V, B3..E3..C3@C3 connector 12Volts

Power Distribution Schematic (Ignition Switch) drawing 642412 E2 @C2 connector J2 12V Ign off, 5.78V Ign on....with Meter connected to J2 backside of fuse block with IGN on...readings went from 6.0V to 6.88V, then I heard the fuel pump build pressure, then I put IGN sw to start and car started while running, meter built up to 9.35V.

Since this schematic shows a direct line of HOT AT ALL TIMES via the IGN Switch, I then went to the PCM C-1 Connector.

Pin 19 initially showed 9V, then climbed to 11.4V, and shows no voltage with IGN SW in off. Pin 63 showd 0 volts no matter what and well as pin 6.
These PCM readings were all with IGN RELAY1 @ rear fuse block installed.
I did do a voltage drop test on F3/C2 with IGN SW OFF 12.40V and with IGN SW ON 11.61V.

I did clean the ground, and double checked those readings, and they were good.

It appears to me the IGNITION SWITCH is faulty, what's your take? Did I cover all the groundwork? I did notice once IGN 1 relay J3 built up voltage car starts right up.....

 

I am assuming that the J3 voltage the same as the 'Rear BEC #41 IGN1 relay' 5.7 voltage from your earlier chart. If so, then I may have misunderstood your chart, because I thought that the voltage was measured at L3 on the control side of the relay, not the power side of the relay. Your earlier chart had a 12V and 11.75V reading. Somehow I got the idea that the 12V reading was from J2 which would mean that the 5.7 volt reading was on Rear IGN-1 Relay connector L3, and is why I thought you had a bad ground. It appears that I misunderstood your chart. Please confirm that the location at 11.75V reading is the switched power at J2 and the 12V reading came from L2 which is consistent with your 5.83-6.12V reading at J3.

There should not be a voltage reading at either J3 or L3 with the Rear IGN 1 Relay pulled. I confirmed this by testing on my car. If the J3 conductor has power then you might have a short to voltage on that circuit. Pull the Rear IGN 1, SIR and VENT SOL fuses and see if you have the 12 volt reading at E2, H3, or R3. If you do, there could be a short to voltage on that circuit, and your ignition switch is probably fine.


Pin 6 should have voltage in start only and is powered from the ignition switch. My guess is that it is working properly, because you have been able to start the vehicle using your alternate procedure. Are you sure you tested it with the ignition at start?

Pin 63 should have voltage in on and start. Since it is powered thru the Hood IGN-1 Relay, it is probable that a short to voltage is causing the relay to malfunction.

My suggestion is to find and eliminate the cause of the J3, (or is it L3?), voltage.

 

You ask some good questions, questions I may have assumed locations. Can you give me the diagram #'s your looking at. I have 2 each, #'s 642412 and the other I cannot read the diagram # which at the top states Power Distribution Schematics (SIR, VENT SOL, IGN 1 fuses and IGN relay).

On the diagram I cannot read #, when I remove IGN 1 relay, only one contact reads 12 volts, which I assume its L2. On the slot right next too it, not underneath it, it reads the 5.66 to 6.12 volts. This is the where the assumption comes in at J3. Now on the backside of the rear fuse box, when I flip it upside down, and meter check contact E2 on C2 fuse block, I get 7 volts, basically the same reading. Once again the assumption is that is J3, since they read the same as when I check the top side of fuse box, yet E2/C2 on diagram #642412 shows that as J2 contact?

When checking the top side of fuse block with IGN relay removed, how do I know what slot is what?

 

The Power Distribution Schematics (SIR, VENT SL, IGN 1 Fuses and IGN 1 Relay) is diagram number 642414.

The Ground Distribution Schematics (G301) is diagram number 642474.

I only have a hard copy of the service manual and can't provide a copy of the diagrams.

There are four contacts located for the Rear IGN 1 relay. Two contacts are for the switched circuit and two contacts are for the control circuit. The contacts representing each circuit are on the opposite diagonal corners. This allows the relay to be installed in both possible orientations and still operate correctly.

L2. The contact that is always hot is L2 from diagram 642414. L2 contains power available for the switched circuit. The relay is the switch.

J3. The contact that is diagonally opposite L2 is J3. It carries switched power to the devices shown on diagram 642414.

J2. The contact that carries around 12 volts when the ignition is on, but does not carry power when it is off is J2 shown on diagram 642412. J2 carries power for the control circuit of the relay. When it has power the relay activates and provides power from L2 to J3.

L3. The contact that is diagonally opposite J2 is L3 shown on diagram 642474. It is the ground circuit. You should not be able to measure significant voltage between L3 and the battery negative terminal regardless of the ignition position. If you can, there is a ground problem in circuit number 750. Use a voltage drop test not a conductivity test. Check position D2 on Fuse Block Rear C1; position D10 on Fuse Block Rear C3; the ground connection for G301; and the wiring on circuit 750.

 

I tried to attach some photo's but could not, also I do have those diagrams you have mentioned. When looking down at the rear fuse block (facing forward) if I understand you correctly... the 4 slots look like this: J-2 LH UPPER......L-2 RH UPPER.......J-3 LH LWR CORNER under J2.....L3 RH LWR CORNER under L2.. So what we have is...L2 reads 12.75 volts consistently....J2.... IGN SW OFF...0 VOLTS.....IGN SW ON...6.70 Volts.....L3....O Volts regardless of ignition sw position.

According to diagram 642412 ignition switch is hot all the time in OFF position, then when placed it ON position that 12Volts should come down to E2/C2 J2 contact, it only builds up to erroneous readings of 5.83 to 6.70. I have witnessed this voltage build up yesterday with meter connected to 7.50V, then I heard the fuel pump build up the required 41 psi of pressure for the car to start, then I turn the ign sw to START and car starts right up just fine.

 

I think I understand what you are saying now, and it is different than my previous two understandings.

Please look at sketch number 144158 and confirm that we are talking about the same conductors. In the text below I provided my third understanding of the location of the voltages you found.

Also, since you earlier had three voltage readings at relay #41, (12V, 11.75V, and 5.70V), please verify the voltage shown as ???.

Sketch number 144158 is a diagram of the Rear Fuse Block in the Body and Accessories chapter of the Cadillac Service Manual. It is titled Electrical Center Identification Views, Fuse Block - Rear. Sketch 144158 shows IGN 1 Relay 41 and, more importantly, the circuit numbers are located.

Circuit number 1 goes to L2. See sketch number 642404. (12.75 volts)
Circuit number 2000 goes to J3. See sketch number 642414. (??? volts)
Circuit number 3 goes to J2. See sketch number 642412. (6 switched volts)
Circuit number 750 goes to L3. See sketch number 642474. (0 volts)

Based on my third understanding of the voltage readings, it looks like a bad ignition switch or a problem with circuit 3. Check B/C1, A13/C200, and E2/C2 before replacing the switch.

One possibility of what might be happening is that if there is a break in circuit 3 either at the ignition, a connector, or a wire, then power could travel down circuit 4 thru the ACCY and Underhood IGN1 Relays and to Rear IGN 1 conductor J2. See diagrams 642412 and 642437. An easy test for this would be to pull the Underhood ACCY relay and verify that the voltage at Rear IGN 1 conductor J2 is zero with the ignition on. This is also consistent with your car not starting because the voltage is diverted from triggering the fuel pump relay in the PCM.

Good Luck

 

To first answer your questions Circuit 1(L2) reads 12.75V, Circuit 2000 (J3) 0V, Circuit 3 (J2) 6V varies, Circuit 750(L3) 0V. I have not yet checked B/C1, A13/C2000 but I have checked E2/C2 prior to you asking. It had 5.83-6.12 volts with IGN sw ON.

Today I checked the REAR IGN 1 J2 with the underhood ACCY relay removed and it does not read 0 Volts with IGN sw ON, it reads what it has been reading 6.7 volts, 0 volts with IGN sw OFF.

I did some other tests with REAR IGN 1 relay INSTALLED and underhood ACCY, IGNITION 1, & START relay removed one at a time.

With ACCY relay removed

IGN SW OFF - circuit 2507-0 volts, circuit 1497 - 0 volts, circuit 1 - 12 volts, circuit 4 - 0 volts
IGN SW ON - circuit 2507 0 volts, circuit 1494 - 0 volts, circuit 1 - 10.40-11.95 volts, circuit 4 10.49-11.85 volts

With IGNITION 1 relay removed

IGN SW OFF - circuit 3 - 0 volts, circuit 1 - 12 volts, circuit 2000 0 volts, circuit 2507 - 0 volts
IGN SW ON - circuit 3 - 6.70-7.45 volts, circuit 1 - 12volts, circuit 2000 - 0.39 volts, circuit 0.01 volts

With START relay removed

IGN SW OFF circuit 542 - 8.70-12.11 volts, circuit 625 0 volts, circuit 575 0 volts, circuit 269 0 volts
IGN SW ON circuit 542 12.12 volts, circuit 625 12.12 volts, circuit 575 0 volts, circuit 269 1.40-2.44 volts

When I checked the 2nd time circuit 542 had a steady 12.40 volts, then I turned IGN SW ON, and circuit 625 read 0 volts at 1st, then I heard the injectors build up pressure and rechecked circuit 542 which read 8.60 volts, & circuit 625 read 8.80 volts.

When you say check B/C1 & A13/C200 it appears B/C1 is right at the IGNITION SW-correct? Where exactly is A13/C200 located? Diagram # ?

How much do I have to tar up to get to switch? is it necessary to remove the radio & all the trim around it?