Hello guys. My father has a 1992 corvette- he has code 46 stored in his pcm and the air conditioner does not work. I remember hearing somewhere that the a/c goes inop with certain codes. Anyway, it would not start so i did the resistor trick below the colum. Now the car starts and has not left me stranded yet (3 days). I cleared all codes with tech 1 as well as through the IPC but code 46 remains. It never actually clears. (also have code 26 and that clears and comes back after about 2min code 26 says diagnose other codes 1st) I have access to alldata and there is no code 46 in their DTC list-- Was thinking about getting a eprom with the vats programmed out but figured id see if anyone has any help--Thanks in advance

 

Code 46 in the Chilton manual says. Personal Automotive Security System (Pass Key II) circuit or Power Steering Pressure Switch (PSPS) circuit.

Before you do all that work on the vats you might try your spare key to see if the problem is in the chip of the key you normally use.

 

Yea ive tried the spare key. Didnt seem to make a difference. Like i said i wired in the resistors to the plug and it started no problem and hasnt left me stranded yet. My only ? is why code 46 doesnt clear at all. i do not have a security light on either. Thanks for your help!!!! i apreciate it

 

Also the more i dig i find out that 92 ECMS didnt even have a code 46??? the unit in it now is a reman. again not sure how i can have code 46 and the vehicle start and run everytime. Im hoping someone out there can shed some light on this for me! thanks again

 

How are you reading the codes? If the code has an H before it that means it is a history code. I suppose it is possible for that code to be from another car that was not removed when it was re manned.

 

Actually it does say. h46 but with the tech1 it comes up current.

 

According to my 1991 fsm, all ecm codes brought up on the instrument cluster will show up as history codes whether current or not.

Mac

 

I have the 1992 Service Manual - according to the book there is no PCM or ECM code 46.

 

Yes i agree %100 this. Thats the problem,Why do i have a code 46 when im not suppose to. And could this be preventing my AC from working??? I command AC on with tech 1 and everything works. PCM is seeing the ac request from programmer. Pressure switch is good. Something is preventing the PCM commanding ac on. So my real ? is will code 46 prevent AC from working??? Or do i need to shotgun a $300 PCM

 

Last night I thought I remembered the Code 46 from somewhere. I was just going through some stuff on my computer, (trying to back some stuff up that I should have done long ago), and I stumbled onto it.
IF you have ever looked at the actual programming on the LT1 PROM - there is a "switch" for VATS Error Code 46. I have it turned off on the PROM I've got. I would expect that since it isn't in the 92 Corvette service manual - it was switched off at the factory. SO ... If you really want to make it go away - reprogramming the PROM Would do it...

As for the A/C not working - It maybe connected - it may not be connected to the code. See if you've got power to the compressor when you request A/C. Hook up a gage set, and see if the system has pressure. If you see something in the 70+ psi range with the system off - that should be enough charge to allow the A/C compressor to engage. If you have pressure, and no power to the compressor - then the issue may be the BCM not allowing the compessor to engage. IF you have sufficient charge, you could try applying power to the compressor clutch and seeing what happens.

GOOD LUCK ...

 

Pressures are good. systems functions normally and blows cold when ac is commanded on w/ tech 1. As far as BCM the wiring diagram i have only shows the programmer and the ECM in it. i am waiting on the 2nd book of the service manual. Can i program the prom myself? or do i have to send it out somewhere??.. Thanks for all your help, its much appreciated

 

Programming the PROM in the OBDI Cars is not as easy as it is in the later OBDII cars where it can be reprogrammed through the OBDII port.

In order to reprogram an OBDI Prom - you need an EPROM Burner - not exactly somethig you can find at Harbor Freight (or evan on a Snap-On Truck). From what I'm told by an Electrical Engineer friend - you remove a piece of "tape" from the PROM and expose it to UV light source - which wipes the memory -then you plug the PROM into the burner - and write the new code via a computer hooked to the PROM. Not exactly DIY stuff.

Give Ed Wright or one of the other LT1 places a call - they should be do it for you - and they can make a number of other changes as well (like changing the fan on/off temps, and for the adventerous - the rev limiter settings).


I've attached the switch settings and the "Constant's table" for a 1992 below.



ECM SWITCH TABLE

0 VATS Diagnostic (Error 46)
0 VATS Select (X = Enabled)
X VSS Diagnostic (Error 24)
0 QDM #1 Diagnostic (Error 26)
0 QDM #2 Diagnostic (Error 27)
0 QDM #3 Diagnostic (Error 28)
0 EGR Diagnostic (Error 32)
X EST Grounded Diagnostic (Error 42)
X Knock Diagnostic (Error 43)
0 A/C Press. Sensor Fail (Error 66)
0 A/C Press. Sensor Degraded (Error 67)
0 A/C Relay Shorted (Error 68)
0 A/C Clutch Circuit Open (Error 69)
0 A/C Evap. Temp. Sensor Fail (Error 71)
X Auto Trans (TCC = O, Manual = X)
X C.A.R.S. Select (X = Enabled)
X Left O2 Sensor Diagnostic (Error 13)
X Left O2 Sensor Lean Diag (Error 44)
X Left O2 Sensor Rich Diag (Error 45)
X Right O2 Sensor Diagnostic (Error 63)
X Right O2 Sensor Lean Diag. (Error 64)
X Right O2 Sensor Rich Diag. (Error 65)


ECM CONSTANTS

Fuel Cutoff Speed 255 MPH
Fuel Resume (Speed) 255 MPH
Fuel Cutoff, 1st Gear (Eng Speed) **** RPM
Fuel Cutoff 2nd Gear (Eng Speed) **** RPM
Fuel Cutoff, 3rd -> 6th Gear (Eng. Spd) **** RPM
Fuel Resume, 1st Gear (Eng Speed) **** RPM
Fuel Resume, 2nd Gear (Eng Speed) **** RPM
Fuel Resume, 3rd -> 6th Gear (Eng Spd) **** RPM
Fan 1 On Coolant Temp, Low MPH 86 Deg C
Fan 1 On Coolant Temp, High MPH 91 Deg C
Fan 2 On Coolant Temp, Low MPH 91 Deg C
Fan 2 On Coolant Temp, High MPH 95 Deg C
Fan Low MPH Hysteresis 4 Deg C
Fan High MPH Hysteresis 5 Deg C
Fan Low/High MPH Threshold 35 MPH
Injector Flow Rate 40 #/HR
Cylinder Volume 780 cc
Maximum Spark Advance 44 Deg.
Knock Retard Enable RPM 650 RPM
Knock Retard Enable Speed 10 MPH
Knock Retard Enable Coolant Temp. -4 Deg. C
Low Octane ESC Retard Enable MAP 69.4 kPa
Low Oct. ESC Retard Disable Delta MAP 11.1 kPa
Low Oct ESC Retard Enable Knock Retard 2.1 Deg.
Low Oct ESC Retard Increase Step Size 50 Counts
Low Oct ESC Retard Decrease Step Size 3 Counts
Throt. Follow Extend Decay Timer (Drive) 50 msec
Throt. Follow Extend Decay Timer (P/N) 62.5 msec
Throt Follower Extend Decay Timer Adder 2 ms/MPH
EGR Off, (TPS) 1.2 % TPS
EGR On, (TPS) 2 % TPS
EGR Low RPM Window, Off RPM 900 RPM
EGR Low RPM Window, On RPM 1000 RPM
EGR High RPM Window, Off RPM 2100 RPM
EGR High RPM Window, On RPM 2000 RPM
EGR Low MAP Window, Off (MAP) 36.2 Kpa
EGR Low MAP Window, On (MAP) 38.8 Kpa
EGR High MAP Window, Off (MAP) 94.2 Kpa
EGR High MAP Window, On (MAP) 93.1 Kpa
EGR On, Vehicle Speed 8 MPH
EGR Off, Vehicle Speed 6 MPH
EGR Enable Cool. Temp. Threshold 147.5 Deg C
Min. Cool. Temp. for Closed Loop 32.75 Deg C
Min Cool Temp for Closed Loop, Cold MAT 59.75 Deg C
Cool Thresh For HighTemp PE TPS Thresh. 116.75 Deg. C
MAP Threshold To Enable Power Enrichment 15 Kpa
Canister Purge Enable MAP Threshold 7 Kpa
Canister Purge Enable TPS Threshold 0 % TPS
Air Injector Enable Cool Temp Threshold 140 Deg C
Minimum BLM Value 108
Maximum BLM Value 160
Min Coolant Temp for BLM Update 40.25 Deg. C
Max Coolant Temp for BLM Update 140 Deg. C
Min MAP for BLM Update 20 Kpa
Minimum Integrator Value 64
Maximum Integrator Value 192
Stoichiometric AFR 14.7 AFR
Fast O2 Rich/Lean Threshold Hysteresis 0 mV
Idle RPM Adder, A/C On 75 RPM
IAC Default Keep Alive Min Position 32 Steps
IAC Minimum Keep Alive Min Position 10 Steps
IAC Maximum Keep Alive Min Position 70 Steps
DFCO Enable RPM Threshold 1400 RPM
DFCO Disable RPM Threshold 1200 RPM
DFCO Enable MAP Threshold 21 kPa
DFCO Disable MAP Threshold 27 kPa
DFCO Disable RPM Decrease Threshold 50 RPM
DFCO Enable Coolant Temp. Threshold 20 Deg. C
DFCO Enable TPS Threshold Hysteresis .4 %TPS
DFCO Enable MPH Threshold 30 MPH
TCC Lock Speed (Low Gears) 42 MPH
TCC Unlock Speed (Low Gears) 40 MPH
TCC Lock Speed (High Gear) 42 MPH
TCC Unlock Speed (High Gears) 40 MPH
TCC Unlock Prevention Speed Threshold 154 MPH
Road Speed Constant 4007 Pulses/Mi
Instrument Panel VSS Pulse Divisor 0
C.A.R.S. Enable Coolant Temp. Threshold 125 Deg. C
Minimum 1st Gear RPM/Vss Ratio 110 Ratio
Minimum 4th Gear RPM/Vss Ratio 30 Ratio
Maximum 4th Gear RPM/Vss Ratio 97 Ratio
PROM ID