LS1 to LQ4 Swap - No Start! Crank Sensor?

[cptinjak]

2bar OS on a 97 vette. P1SC procharger, stock engine. All that was changed was the longblock, from a stock LS1 to a stock LQ4.

I cannot get the engine to fire. It will crank all day, but I cannot get any RPM readings, (or much else, for that matter) on the scanner. Is this a sure sign of a bad crank sensor? Really don't want to take this car back apart again, but I think I might not have a choice here. I'm getting that sinking feeling...

Any insight would be greatly appreciated.

Jack

[Montecarlodrag]

I see no RPM, no injector pulse, no MAP reading and no timing advance.
I think the Crank sensor may be bad. Do another datalog to see if it sends any signal, there is a PID to do it.

Pull a plug wire and put a used spark plug into the boot, with the ground strap of the plug touching the alternator case have somebody crank the engine. You should see the spark. If not, the crank sensor is bad or the wiring was damaged when the engine was changed

[cptinjak]

I see no RPM, no injector pulse, no MAP reading and no timing advance.
I think the Crank sensor may be bad. Do another datalog to see if it sends any signal, there is a PID to do it.

Pull a plug wire and put a used spark plug into the boot, with the ground strap of the plug touching the alternator case have somebody crank the engine. You should see the spark. If not, the crank sensor is bad or the wiring was damaged when the engine was changed

There is definitely no spark.

Thanks for the tip. I didn't realize there was already a PID for the crank sensor. I'll try that now. Do you know what kind of voltage I should be seeing at each pin of that connector? I doubt that any damage was done during the swap, but this car has some questionable past work done, (o2 wires partially melted, etc.) so I would like to rule out the wiring if possible.

Thanks,

Jack

[cptinjak]

Logged again. Included the Crank Sensor PID this time. Not showing anything at all. I have a sensor ordered and I'll pick it up tomorrow. I hate waiting around for parts. This car needs to GO! This has been the engine swap from hell, but that's what you get when the owner buys junkyard shit, I suppose.

Does anyone know what I should be seeing at each pin of that connector during cranking? I would like to put a meter on it but not sure what I should be looking for at each pin.

Thanks,

Jack

[Montecarlodrag]

Logged again. Included the Crank Sensor PID this time. Not showing anything at all. I have a sensor ordered and I'll pick it up tomorrow. I hate waiting around for parts. This car needs to GO! This has been the engine swap from hell, but that's what you get when the owner buys junkyard shit, I suppose.

Does anyone know what I should be seeing at each pin of that connector during cranking? I would like to put a meter on it but not sure what I should be looking for at each pin.

Thanks,

Jack

You need an osciloscope to see the signal CKP sensor sends. Is something like this:




However you can check if the wires are good using a multimeter.
Green wire goes to PCM pin #62
Yellow/Blk wire goes to PCM pin #22
Blue wire goes to PCM pin #44

Remove PCM from harness, also unplug sensor. Check continuity from sensor's connector to PCM's connector.
Check resistance between them and between ground, there should be open circuit (infinite resistance)
If you find any shorted or open wire, that's the problem.

I have done a lot of engine swaps, most of the times I had a crank sensor problem was caused by bad wiring, only 1 time was a bad sensor.

Test the harness before buying a new sensor.

[cptinjak]

You need an osciloscope to see the signal CKP sensor sends. Is something like this:

However you can check if the wires are good using a multimeter.
Green wire goes to PCM pin #62
Yellow/Blk wire goes to PCM pin #22
Blue wire goes to PCM pin #44

Remove PCM from harness, also unplug sensor. Check continuity from sensor's connector to PCM's connector.
Check resistance between them and between ground, there should be open circuit (infinite resistance)
If you find any shorted or open wire, that's the problem.

I have done a lot of engine swaps, most of the times I had a crank sensor problem was caused by bad wiring, only 1 time was a bad sensor.

Test the harness before buying a new sensor.

Thank you so much for the pinouts. I will test it and let you know what happens.

Jack

[cptinjak]

Remove PCM from harness, also unplug sensor. Check continuity from sensor's connector to PCM's connector.
Check resistance between them and between ground, there should be open circuit (infinite resistance)
If you find any shorted or open wire, that's the problem.

I have done a lot of engine swaps, most of the times I had a crank sensor problem was caused by bad wiring, only 1 time was a bad sensor.

Test the harness before buying a new sensor.

All three show continuity and none are grounding out. Guess I'm doing a sensor for sure. That means the header is coming out, and maybe the starter too. Not sure If I can get around that.

Thank you again for your help.


Jack

[miker2]

ok,i'll confess that i had a similar problem a year ago on a 6.0 liter swap. turned out i had swapped the oil level and crank sensor connectors and of course,it wouldn't start. found the problem when i looked at wire colors.

[cptinjak]

ok,i'll confess that i had a similar problem a year ago on a 6.0 liter swap. turned out i had swapped the oil level and crank sensor connectors and of course,it wouldn't start. found the problem when i looked at wire colors.

Oh yea, they are the same connector type aren't they? I can see that being a pain to diagnose! Luckily I have continuity to the correct pins on the PCM connectors.

Jack

[cptinjak]

However you can check if the wires are good using a multimeter.
Green wire goes to PCM pin #62 ON THE BLUE CONNECTOR
Yellow/Blk wire goes to PCM pin #22 ON THE BLUE CONNECTOR
Blue wire goes to PCM pin #44 ON THE RED CONNECTOR

Just to clarify in case anyone else sees this in the future!

Jack

[Montecarlodrag]

Just to clarify in case anyone else sees this in the future!

Jack

Yes I forgot to say that.
If wiring is good, the sensor is bad.

The easiest way to change the crank sensor is taking out the starter, but some headers make it very difficult

[cptinjak]

Yes I forgot to say that.
If wiring is good, the sensor is bad.

The easiest way to change the crank sensor is taking out the starter, but some headers make it very difficult

Just got the sensor in. This car has cheap OBX headers that dont fit well and I can't drop out with the engine in place, so that was fun...Debating whether to go to bed or bolt the header up and see if it starts...

Jack

[cptinjak]

Sooo....

Got the new sensor in after testing harness continuity. Still not getting anything at all on the scanner. No RPM signal. Nothing coming from the Crank Sensor PID either.

Sigh... Anyone have any more ideas?

Jack

[Montecarlodrag]

Do you have access to another PCM to test? It would save you a lot of time, because sometimes the PCM is bad and it won't start. You can flash it, scan, everything, it only won't start

[cptinjak]

Do you have access to another PCM to test? It would save you a lot of time, because sometimes the PCM is bad and it won't start. You can flash it, scan, everything, it only won't start

I do not, and I certainly am not going to pay to license another PCM. I'm already $300 into this job out of pocket, and the owner has my car at the moment to make it worse! lol

I pulled the codes. It showed B2592 along with RTD NO COMM. That means the BCM is looking for Selective Ride Control, which this car does not have. This leads me to believe maybe the BCM has been swapped at some point, and disconnecting the battery during the engine swap somehow reset the BCM? I don't have a Tech II, so I have no way of getting to the BCM to look.

:/

I appreciate your help thus far Monte. It means a lot.



Jack

[Montecarlodrag]

Glad to help.

With all you have done it should start. I'm starting to suspect the reluctor in the new block.
Check if the sensor has 12V at green wire with ignition key open (meassured at the sensor's connector)

Buy a crank sensor connector, plug it to the sensor (installed in the engine). Feed 12V to the green wire.

With a multimeter, set it to DC volts and hook the red lead to blue wire, black lead to ground.
Loose all spark plugs.
With a ratchet on the damper bolt, slowly turn the engine clockwise and watch the multimeter. It should give you pulses of 5V, if you continue to rotate the engine you should see 0V-5V-0V-5V
If you get no pulses (only 0 Volts) then there is a problem with the reluctor.

With sensor unbloted from engine block you can simulate the pulses, with a magnetic metal in front of the sensor it should send 5V, 0V without it.

[cptinjak]

Glad to help.

With all you have done it should start. I'm starting to suspect the reluctor in the new block.
Check if the sensor has 12V at green wire with ignition key open (meassured at the sensor's connector)

Buy a crank sensor connector, plug it to the sensor (installed in the engine). Feed 12V to the green wire.

With a multimeter, set it to DC volts and hook the red lead to blue wire, black lead to ground.
Loose all spark plugs.
With a ratchet on the damper bolt, slowly turn the engine clockwise and watch the multimeter. It should give you pulses of 5V, if you continue to rotate the engine you should see 0V-5V-0V-5V
If you get no pulses (only 0 Volts) then there is a problem with the reluctor.

With sensor unbloted from engine block you can simulate the pulses, with a magnetic metal in front of the sensor it should send 5V, 0V without it.

I was pretty worried you'd say reluctor. I didn't notice anything wrong with it when I had the oil pan off, but then again, I wasn't looking for anything either... :/

Jack

[miker2]

did you check to see if all of your ground wires were reconnected ?

[93camaro_zzz]

Yeah, I would also check what Miker said. It sounds simple, but one time I had a no start condition. Pulled a plug, and it was getting no spark. Turned out that it was a ground I had forgotten.

The coil packs have a ground, and it should be at the back of the motor. Pretty much right behind the drivers side valve cover.

I hooked mine back up, and wah-lah, my engine started.

[cptinjak]

Got it sorted out! I had a second pair of eyes go through things. He found that the ground near the starter wasn't connected properly. Felt kind of foolish, but at least the car is running!

Thank you everyone for your help. Sorry for sending you on a wild goose chase!

Jack