Hi, I'am new to posting. I have only looked up in the posts but now I need some expert advise. Bear with me if I don't proceed correctly. This will be a OJT session for me. I have a 2001 C5. Sometime ago I started having an issue with starting. The starter works fine. The engine will turn over but won't start. It may run at a low RPM roughly and when you step on the pedal it does nothing. I turn off the key and cycle the key to on and off a few times and then it will start. I may start several times and no issues. I've learn to listen for the fuel pump to activate for the 2 second period. When this takes place I know it will start. When I don't hear the pump activate naturally it won't start. I've checked out the electrical circuit from the fuse block under the hood all the way through the fuel pump to the ground and it tests fine. I can manually run the pump without any problem by bypassing the relay, all works fine. I do not have a check engine light and no fuel pump codes.Once I have it started the car runs fine. The engine has never cut out when driving. I always have it in the back of my mind if I go any distance this issue may accrue and I won't get it started and then I'am stuck. I've even cleaned the key, and put a new battery in the FOB. So far all is well not to say it could happen again. I've read in the threads about ignition issues and having to clean off the contacts, but I have not gone that far yet. If anyone can shed some light on the issue I would love to hear from you. Thanks ahead of time, Jim

 

Have you checked what codes you are getting when the problem occurs?

Here is how to do it if you don't know. Once you get the codes post them here.

https://ls1tech.com/forums/corvette-...they-mean.html

 

Yes the DTCs will get you on the correct line to repair. I also have an 02 and I have experienced the same issue. I figured it out and I hope you have the same easy fix.

When you read the DTCs look for a bunch of NO COMMUNICATIONS messages. When I have my issue, My 02 Z will crank but the engine will not run.

My problem is related to a serial data buss issue. The drivers and passengers door wiring harness (SIX PIN) power plug has damaged female pins and causes the module to turn ON and OFF . This corrupts the serial data buss and the comms link between the BCM and PCM. Sometimes you will see that the drivers and or passengers door widow will not work when this happens.

Reading the DTCs will shed a lot of light on what you need to do next!!

Bill

 

Hi Jim !!...follow Bill’s advise and see what happens !!...if good see if the Tach appears to move when you try starting it...if not it may be a crank sensor issue...if the sensor is bad you will not have spark (that’s why you look at the Tach...if you have spark the Tach should be moving a little bit...if it’s hard to see just have someone crank the engine and remove the plug wire at the coil pack and keeping the plug wire about 1/2 inch from the coil pack see if the spark is visible...also with a bad crank sensor you don’t have injector pulse... AND if the crank sensor is bad you will not hear the fuel pump prime...you can verify this by removing the fuel pump relay and with a 12 volt test light connected to battery negative when the key is turned on you should see the test light illuminate for 2 seconds and shut off when you are connected to pin 86 (see pic)...also thinking it may be a bad ignition switch...connect a voltmeter to battery positive and connect the negative lead to one of the 2 test points on top of fuse 17 ( THROTCONT)...the power that feeds the fuse and a lot of critical circuits (fuel injectors, coil packs, MAF sensor, fuel pump)...turn the key ON and see what you read...should not be more than .1 to .2 volts...see what you have...if the PCM is receiving low voltage it can not send out a 12 volt reference to other circuits not mentioned like the crank sensor which needs 12 volts to operate correctly !!

 

Hi Rebel & Bill, I'll try this again from the beginning. I lost power for a few minutes from a storm passing through and my reply I had typed was lost so I'am starting over. I had cleared all the codes the other day but had run the car over the weekend. I just checked for codes and the BCM had one code which was B0432H, the rear defogger relay circuit. The other two codes were HVAC codes B0361H, Left Actuator Feedback Short to GND & B0338 H & C Inside Air Temp Sensor Open. Did not see a bunch of NO COMMUNICATIONS messages. Never had a issue with the driver or passenger door windows not working. The engine will always crank but won,t run when this issue takes place.

Jim

 

Those DTC’s will NOT cause a cranking no start !!

 

Hi C5 Diag, I question the crank sensor issue. Does the crank sensor either work or not work? When I turn the key to on and I don"t hear the fuel pump run I know it won"t start when I crank the engine over. What I do is turn the key off and on two or three times in a row without cranking the engine. Then I try cranking it. If it doesn't start again I repeat procedure and cycle my off and on of the switch to maybe five, six or seven times. It has always started at some point. When it starts and I'am driving it has never stopped until I turn the key off. I've tried the fuel pump relay test and the light goes out after two seconds. I've run the pump by bypassing the relay so I know the wiring is good all the way to its ground. To try the ignition test I'll have to do this when the issue happens at home and I have my test tools. This starting issue is a hit and miss thing. Luckily more of a hit then a miss. I've read Bill Curlee's post on cleaning off the ignition contacts but haven't done it yet. Probably would not hurt because I have 108,000 miles on the car. I appreciate the all the reply's from you fellows. I don't give up. With everyone's help I'll get to the bottom of this.

Thanks Again, Jim

 

Yes a CKP can sometimes be intermittent and gets worse with the engine hot (high resistance) but cycling the key like you are doing and then it starts up makes me believe it may be an ignition switch problem and the PCM needs 12 volt to make the crank sensor operate correctly...so it’s really not the sensor but the reference voltage that is fed into it OR the sensor too...like I said try the voltage drop check on the THROTCONT fuse or even the PCM B fuse 23..that feeds the crank sensor ...you also said you bypassed the fuel pump but did you check the voltage ??...there is no voltage number in my FSM and yours is an ‘01 like mine for the voltage needed to operate the crank sensor correctly...I use the 90-10 engineering rule for this sensor...based on 12 volts it should be more than 90% and must be less than 10% when the signal wire is pulled to ground...it produces a 0-12 volt square wave so maybe anything from below 1 to more than 11 volts may be a good for it to operate...did you check pin 86 with the test light when it DIDN’T start ??

 

Here’s a great video about the crank sensor and what I was talking about the voltage...you would have to check the signal wire at the PCM and if low you would then unplug the sensor..if the signal wire goes to 12 volts it’s a bad sensor..,now getting unplugged is a WHOLE different story due to its location !!...had a Forum member who was having this issue and we had only 2 volts or so at the PCM crank feed wire and at the crank sensor so I’m thinking it’s a bad PCM but when I had him disconnect the CAM sensor the 12 volts came back...the cam and crank 12 volt feed are on the same circuit internally inside the PCM...that diag was a interesting one...LOL !!

 

I think i"ll tackle the ignition switch this weekend and see if that fix's the problem. I've had to get into the dash before so I don't see that as a problem. I didn't bypass the fuel pump I bypassed the fuel pump relay by jumping from #30 to #87 with the key on and the pump ran. Did not check any voltage. I would like to check pin #86 when it won't start but that is hard to do because it may start when I try again with the test light on pin #86. At least I can drive it and not worry about it dying. What I worry about is not getting it started when I'am any distance from home. Thanks Again for all the ideas. JIM

 

It may not be an ignition switch problem but maybe the crank sensor...without doing a little testing you’ll only be firing that “parts canon” !!...good luck !!

 

We'll give both a shot. I'll keep you posted. Thanks Jim

 

I did the fuel pump test by going from the battery negative to pin #86, turned key on and the light lit for 2 seconds so I know the crank sensor is good. The I did the voltage test from battery positive to fuse # 17 got a reading of .2 volts. I did swap the relay from # 35 (pump slot) to # 36 (horn slot) and I have not had a starting issue as of yet. I drove and started the car several times and no starting issue took place. I did go to O'Reilly's and purchased a new relay and put it in the # 36 (horn slot) after driving it for 50 miles with several start ups. Sometimes you go full circle to find a very simple fix. Thanks again for all the ideas and help. I'll give it the time test and see what happens.This is a GREAT forum.

Jim

 

Jim, great to hear it’s running ok !!...yes, checking that the test light lit for 2 seconds ruled out the crank sensor and the .2 volts told us the ignition switch was good...those relays take a beating sometimes but swapping them with another is sometimes the easiest way to diagnose !!

 

Thanks C5 Diag, I love to drive it, so we'll see how it goes. Going out on a nice cruise on the 12th of Aug with a fellow Vette friend couple. Hope it is ok. Hopefully I don't have an issue but if I do I'll keep you posted. Thanks again.

Jim

 

Back again, we went on the 100 mile cruise with our corvette friends. Had no trouble at all with starting the car. Have had no trouble for quite awhile. I think the problem is licked. Sure glad I did not go through the ignition switch procedure. Thanks again for all the help you people gave me. I'am back on track and feel I know a little more about the car now.

Thanks for this wonder web site, Jim