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Dan
Dan, Technician
Category: Chevy
Satisfied Customers: 21476
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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2004 chevy impala: crank..i turn my key but the engine wont start

Resolved Question:

I'm having a problem with my 2004 chevy impala. My dad and I have spent numerous hours this week trying to get it running. The engine will crank when i turn my key but the engine wont start. We've tried replacing the ignition switch, which had voltage. We've checked the electronic ignition control module at our local auto parts store, which was working fine. There is no visual sparks along the plug gap in the spark plug. The chilton manual led us to believe that the crankshaft sensors may be the problem. We only checked the 7x crank sensor (I have a 3.4 L engine).
The random times that i can start my car. it dies within seconds. We just rented a scan tool and plugged it up but to no avail, the unit told us that the car had no codes or errors. The security light is on and it could be the Passlock II system, but would that prevent voltage from going to the spark plugs?

Lack of spark seems to be the reason why the car won't start but we've looked everywhere and taking it to the dealer is the final decision. Much help would be appreciated.
Submitted: 2 years ago.
Category: Chevy
Expert:  Dan replied 2 years ago.

did you replace electrical part of ignition switch or lock cylinder?

Customer: replied 2 years ago.
Just the lock cylinder, but we replaced the ignition switch initially,did the 30 minute procedure, found out that the car started fine and we didn't need the cylinder, so we took it out and put the original back in. The car seemed fine, drove it around town (with the security light still on), and it worked fine for the rest of the day. The following days it started twice but died instantly, while the security light is still on, and now it seems it won't hardly crank.
Expert:  Dan replied 2 years ago.
Is this orignal reason you replaced ignition switch? Did security light go out with new lock cylinder? Did you do relearn?
Customer: replied 2 years ago.
My car stalled and died twice while i was out driving. I had to wait a specific amount of time to start my car. I told my dad, after doing internet research, that I thought the reason was the ignition switch. That's why we replaced that first. The security light, after doing the 30 minute relearn process, did go out ( We believe, i honestly don't remember), BUT then dad pushed a connector plug, that's on my battery, in and the car started 5 times in a row, so we thought that a loose connection was the problem, Thus is why we put back in the original ignition cylinder, and THEN the security light came on. Didn't seem to matter at the time, thats when i then drove the car around town, with the security light on, and it seemed fine for that day. I have not done the relearn process again after installing the original ign. cylinder.
Expert:  Dan replied 2 years ago.
The cylinder itself is the most common cause and considering you think light was out with new cylinder I would install the new one again.
Customer: replied 2 years ago.
Relist: Answer quality. I would like someone who responds in complete sentences and with a little bit more detail.
Expert:  Dan replied 2 years ago.
The lock cylinder is the most common thing to fail and since light come on after reinstalling old lock cylinder but was off before tells me the lock cylinder is bad...Access the Passlock sensor 3-wire connector. This is located in the ignition lock cylinder housing. Leaving the connector plugged in, check for 12 volts on the White wire and 0 volts on the Black wire. This is the power and ground provided by the Body Control Module (BCM). Disconnect the 3 wire connector. Check for 5 volts on the Yellow wire sent from the BCM. Reconnect the connector, verify the voltage drops to the same voltage every time as the ignition is turned on and to crank. Do this 3-4 times in a row. Verify the voltages are always the same. If the voltages are different, verify the BCM sends out a steady 5 volt reference on the Yellow wire. If OK, replace the lock cylinder and lock cylinder housing.
Customer: replied 2 years ago.
I have few concerns with this:
-What you're saying is that a defective lock cylinder will keep the spark plugs from sparking?
-Also, i noticed an "ON/OFF" switch in my driver-side fuse box. I strongly believe that this is this..http://newsgroups.derkeiler.com/Archive/Rec/rec.autos.tech/2006-02/msg00104.html
Would this switch effect the procedure you gave us? Also, dad believes that a new lock cylinder won't start the engine, since the old one didn't, unless we need to replace the housing unit as well?
Expert:  Dan replied 2 years ago.

The lock cylinder causes no injector pulse...To find out if its spark or injector pulse related see if vehicle will run on starting fluid if so its injector pulse related. Yes you need to replace the lock cylinder and housing "where wires go into".

Customer: replied 2 years ago.
My father has been working on vehicles for many years, though he is not a trained mechanic. He removed a spark plug, grounded it out, and while i cranked the car no spark would jump the gap during cranking. So he strongly believes it is spark related. Any thoughts? (sorry we're not trying to argue with you, just trying to get the car fixed :) ).
Expert:  Dan replied 2 years ago.
I would see if it runs on starting fluid just to be sure if not next step is to check pink for power, black for ground, yellow and purple wires for ac voltage while cranking from crank sensor...If all of those are good but no spark relace ignition module. But the lock cylinder is common to fail causing security light to come on and a start/stall condition.
Customer: replied 2 years ago.
Tests Performed:
1. Verified 12 vdc from pink wire to ground.
2. Verified 200 mv signal from 7x crankshaft sensor.
3. Removed ignition module. Took to Auto Zone. Showed good on their testing after 12 consecutive trys. (Still doesn't mean it's bad though).
4. Re-installed all devices and still no spark on plugs.

What should we do from here? (Besides the starter fluid)
Expert:  Dan replied 2 years ago.
Sensor should have(NNN) NNN-NNNNohms and should also be putting out 800mv so it sounds like crank sensor is bad but I would double check if it runs on starting fluid so your 100% sure iit is a spark problem.
Customer: replied 2 years ago.
We re-checked the sensor with the selector switch set to Ohms. It came back as 877 ohms so the sensor is good. We did the starter fluid 3 times and it would not start. What's next?
Expert:  Dan replied 2 years ago.

I would replace crank sensor as voltage it is putting out while cranking seems to be low..it should be putting out around .7v ac voltage while cranking.

Customer: replied 2 years ago.
we rechecked it with the reader on ac voltage. We got 1.5v ac when cranked 6 times. Any suggestions now? (The chilton manual originally had us checking milivolts) If the sensor(s) is/are bad, should we replace the 7x and/or 24x ?
Expert:  Dan replied 2 years ago.
If you have good gound on black, power on pink while cranking, then I would replace ignition module even though it is testing good because from what we are hearing it should be running...You can disconnect 5 in connector and see if it runs...If not replace ignition module.
Customer: replied 2 years ago.
"You can disconnect 5 in connector" Can you be more specific?
Expert:  Dan replied 2 years ago.

There is a 5 pin connector that plugs into the ignition module...Disconnect it from ignition module to see if it runs..If not replace ignition module.

Customer: replied 2 years ago.
We did disconnect it from the module. The car still wouldn't start. The crank sounded different though (We're also afraid the fuel flooded). Your recommendation is to now replace the ignition module, although it ran as good? After i do that, i'll still need to get the security telltale of my screen. Should i do the relearn process again as well?
Expert:  Dan replied 2 years ago.
Security system would only cause no injector pulse so if you have no spark then problems are unrelated..You can check oil to see if it looks flooded if so change oil but yes I would replace ignition module at this point if oil is not flooded.
Customer: replied 2 years ago.
We, once again, tested the ignition module and it was working. The guy at auto zone says the most common problem is that the crankshaft sensor, 24x i believe, is bad. We're are going to purchase the part next week and try to fix it then. Could you upload schematics showing how to replace the 24x and 7x crankshaft sensors? After that, i think we'll be satisfied lol.
Expert:  Dan replied 2 years ago.

Here are replacement instructions for crank sensors.

 

http://db.tt/DY564NW

 

http://db.tt/UHmu367
Customer: replied 2 years ago.
Thank you. A few more questions, sorry. If the 24x sensor goes bad will the engine not run? Or is that just with the 7x? Also, could there be a possible problem with the PCM in where we'd have to replace it?
Expert:  Dan replied 2 years ago.

If 24x was bad it should run with 5 pin connector disconnected from ignition module so since it doesnt I do not think that is the issue...Also if it was a problem with pcm it should run with conector disconnected..so it sounds like a 7x crank sensor and/or ignition module is the problem.

Customer: replied 2 years ago.
Thanks so much for your time Dan. I really hope we can get it worked out shortly!
Expert:  Dan replied 2 years ago.
Happy I could help, let me know if you end up running into questions or what fix is. You can reply to this answer at any time even after you click accept without any additional fee's. Thanks
Dan, Technician
Category: Chevy
Satisfied Customers: 21476
Experience: Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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