cpetruzzi

I'm trying to find an intermittent electrical problem and my scanner recently showed a 5-volt reference 1 value of zero. Referece 2 was fine at 5 volts. I guess this indicates a short somewhere in the reference 1 circuit. Does anyone know which sensors are on that circuit. The TP and APP sensor readings also looked weird so that's where I'll start looking. I'm thinking that when the tests are run for this circuit, that's when the car stalls but I assume the TP & APP values are monitored continuously, but I'm not sure.

Any help is greatly appreciated.

jft69z

If you're asking about a 2008 vette as in your profile (it's always easier if you include that info in your post),

The sensors on the +5V1 are:

MAP sensor, CMP (cam position), FTP (fuel tank pressure), EOP (engine oil pressure), A/C refrig. pressure, APP (accelerator pedal position, this uses both 5V1 & 5V2 signals ).

+5V2 has:

Other half of APP, CKP (crank position sensor), and throttle body.


Any history DTC's?

cpetruzzi

Thanks for the quick reply. Yup, I forgot to mention it's an '08 coupe with M6 & NPP. Also, the main DTC is P0601 plus some other C and/or B codes. Most of the codes have gone away since I've cleaned most connectors, bought a new battery and applied many curse words. Last time it just would not start for a few minutes and then it was fine and has been fine for a couple of weeks. I'm waiting for the next issue each time I get in the car because I have not come up with any obvious problem so far.

jft69z

P0601 is for a TCM (transmission control module) "ROM test failed 5 or more times" code. Seems kind of an odd code for a manual trans car...

Have you cleaned up all the grounds, etc?

If it comes back maybe try to jot down all the other codes before clearing or pulling battery cable.

cpetruzzi

Joe T,
First of all, I love the pic of your '69 Z-28! I had one in 1971-1973 and I still miss it.

Here's the freeze frame data from the last no-start issue.

Trouble Codes
P0601 $07E8
Internal Control Module Memory Check Sum Error

Freeze Frame
DTC that caused required freeze P0601
frame data storage

Fuel system 1 status CL

Fuel System 2 status CL

Calculated Load Value 24.7 %

Engine Coolant Temperature 189 °F

Short Term Fuel Trim -Bank 1 -2.3 %

Long Term Fuel Trim - Bank 1 10.2 %

Short Term Fuel Trim -Bank 2 -5.5 %

Long Term Fuel Trim - Bank 2 7.0 %

Intake Manifold Absolute Pressure 5.2 psi

Engine RPM 708 rpm

Vehicle Speed Sensor 0 mph

Ignition Timing Advance for #1 5.5 °
Cylinder

Intake Air Temperature 113 °F

Air Flow Rate from Mass Air Flow 0.02 lb/s
Sensor

Absolute Throttle Position 16.5 %

Time Since Engine Start 1534 sec

Commanded Evaporative Purge 20.8 %

Fuel Level Input 61.2 %

Number of warm-ups since 5
diagnostic trouble codes cleared

Distance since diagnostic trouble 51 miles
codes cleared

Evap System Vapor Pressure -0.492 inH2o

Barometric Pressure 14.5 psi

Catalyst Temperature Bank 1078 °F
1,Sensor 1

Catalyst Temperature Bank 1132 °F
2,Sensor 1

Control module voltage 13.521 V

Absolute Load Value 18.0 %

Commanded Equivalence Ratio 0.999

Relative Throttle Position 5.9 %

Ambient air temperature 82 °F

Absolute Throttle Position B 15.7 %

Accelerator Pedal Position D 20.8 %

Accelerator Pedal Position E 10.2 %

Commanded Throttle Actuator 7.5 %
Control

jft69z

Thanks, I think of selling it sometimes but know I'd miss it. 454 LS6 big block motor with aluminum heads, roller cam, 5 speed, etc. A tire punisher for sure.

Freeze frame data looks pretty uneventful, maybe a little bit of difference in the APP comparisons.

So that code is still present? Or has it been off for a few weeks as mentioned in post 3, or just the rest of the numerous codes?

EDIT: So I did a little more checking. The initial data I gave you regarding P0601 relating to the transmission was misleading. I used Alldata at the time, which is sometimes faulty. I looked in the actual GM eSI procedures and it says that code can be set in the TCM (trans module), FPCM (fuel pump control), or ECM. S0oooo, looking at the ECM info paints a different picture. THAT one relates to the APP, go figure. I'll include that info as attachments so you can see if it makes sense.

Sometimes Alldata leaves critical bits of info out, usually at the most inopportune times, sorry.

cpetruzzi

This week I'll try to check the wires from the accelerator pedal to look for signs of any shorts. I don't know what else to do for now.

Thanks for your help Joe.

jft69z

Looks like you have access to a scan tool. If you do, I'd maybe start with graph mode of anything associated with the APP signals, throttle, etc. KOEO (Key on, engine off), compare APP1 & APP2, run the pedal thru it's range and monitor for drop-outs, glitches, big differences, etc. Just a thought....

Good luck & let me know if you need more schematics or service manual info.

Joe

cpetruzzi

Good idea. I'm just learning how to use the scanner so I'll try running a graph of APP &TP sensor readings. Maybe 5-volt references too.

Carmen

cpetruzzi

Joe,

I ran a graph of APP position and and TPS position with KOEO and it looked fine. As I stepped on the pedal both items increased accordingly.

Then I started th engine and graphed APP position and voltage. This time the APP position stayed at zero while the voltage increased as I revved the engine. I wasn't able to print the results but I'll keep testing and next time I'll take a picture of the graph. I guess it could be a bad APP sensor or a short somewhere in the circuit.

Carmen

jft69z

Hey Carmen, sent you a PM.