Home Made obd scanner ??

[iroc12valve]

on my 1991 crew cab (square body like a suburban) it is running like a diesel and the check engine light is on, I remember someone telling me that on safari's up to 1995 you could use a short piece of wire to jump the connectors where you would normally plug in a scan tool and then the engine light would flash xx many times slowly and then xx many times quickly ( like morse code almost) which would give you a code # (for example 2 long then 3 short for # 23)
I assume this works on the trucks too but i dont remember the exact spots to "jump"


Also if any one has a link to how to decipher the codes E.G. code 23 bad ign coil, that would be much appreciated

[63chevyll]

stick a paperclip in the A and B terminal on your OBD connector under the steering wheel,

while looking at it, A will be the upper right, and B will be the one just next to it, to the left,

turn key on, and start counting the enging light

[BLE 'BURBAN]

Originally Posted by 63chevyll

stick a paperclip in the A and B terminal on your OBD connector under the steering wheel,

while looking at it, A will be the upper right, and B will be the one just next to it, to the left,

turn key on, and start counting the enging light

When doing this, DO NOT START THE VEHICLE!!!

Each code will flash 3 times before moving on to the next code.
First and last code to flash will be code 12 which will be *(pause)** (long pause) *(pause)** (long pause) *(pause)**
a bit of a longer pause will happen before the next trouble code will flash, again 3 times. Once all trouble codes have flashed it will flash code 12 again.
It'll continue to do this as long as you have the key turned on and the paperclip plugged into terminals A & B.

Heres a listing of the codes I found online for ya.

GM OBD-1 Diagnostic Trouble Codes

For 1995-previous model year EFI-equipped GM vehicles. NOTE: Some codes not supported on all models, consult your specific vehicle's service manual for the correct trouble code list and description for your application.

DTC - 12 No distributor reference pulse (diagnostic test active)

DTC - 13 Oxygen sensor circuit open or no activity

DTC - 13 Left bank O2 sensor circuit open or no activity

DTC - 14 Engine coolant temp sensor error (high temp indicated)

DTC - 15 Engine coolant temp sensor error (low temp indicated)

DTC - 16 System voltage too low

DTC - 17 Camshaft position sensor error

DTC - 21 Throttle Position sensor error (signal high)

DTC - 22 Throttle position sensor error (signal low)

DTC - 23 Intake air temp sensor error (low temp indicated)

DTC - 24 Vehicle speed sensor error (open circuit or no activity)

DTC - 25 Intake air temp sensor error (high temp indicated)

DTC - 26 Quad Driver Module (QDM A) error

DTC - 28 Auto transmission range pressure switch error

DTC - 31 Wastegate solenoid circuit error

DTC - 31 Gear Position Switch (PRNDL) error

DTC - 32 EGR system failure

DTC - 33 MAP sensor circuit error (signal high indicating low vacuum)

DTC - 34 MAP sensor circuit error (signal low indicating high vacuum)

DTC - 35 IAC problem or idle error

DTC - 36 MAF sensor error

DTC - 36 24x Crankshaft position sensor circuit error

DTC - 36 4T60-E Shifting Error

DTC - 37 TCC brake switch circuit error

DTC - 38 TCC brake switch circuit error

DTC - 39 Clutch switch circuit error

DTC - 39 TCC error

DTC - 41 Ignition control error

DTC - 41 MEM-CAL error

DTC - 41 C³I Cam Sensor Signal error

DTC - 42 Ignition bypass circuit error

DTC - 43 Knock sensor error

DTC - 44 Oxygen sensor error (lean condition indicated)

DTC - 44 Left bank O2 sensor error (lean condition indicated)

DTC - 45 Oxygen sensor error (rich condition indicated)

DTC - 45 Left bank O2 sensor error (rich condition indicated)

DTC - 46 Pass-Key II (VATS) system error - circuit out of freq range

DTC - 47 UART (serial data) circuit error

DTC - 51 PROM error

DTC - 51 Incorrect MEM-CAL

DTC - 52 Fuel cal-pak incorrect or missing

DTC - 53 System voltage too high

DTC - 53 Digital EGR Valve solenoid 1 error

DTC - 54 Fuel pump circuit low voltage

DTC - 54 Digital EGR Valve solenoid 2 error

DTC - 55 ECM error

DTC - 55 Digital EGR Valve solenoid 3 error

DTC - 56 Quad Driver Module (QDM B) error

DTC - 57 Boost Control error

DTC - 58 Trans fluid temp sensor circuit error (low voltage)

DTC - 58 VATS system error

DTC - 59 Trans fluid temp sensor circuit error (high voltage)

DTC - 61 A/C system performance

DTC - 63 Right bank O2 sensor circuit error

DTC - 63 MAP sensor circuit signal voltage high (low vacuum indicated)

DTC - 64 Right bank O2 sensor lean exhaust indicated

DTC - 64 MAP sensor circuit signal voltage low (high vacuum indicated)

DTC - 65 Right bank O2 sensor rich exhaust indicated

DTC - 66 A/C pressure sensor circuit error (low pressure indicated)

DTC - 67 A/C pressure sensor circuit error

DTC - 68 A/C clutch relay circuit error (shorted to ground)

DTC - 69 A/C clutch relay circuit error (open circuit indicated)

DTC - 69 A/C high pressure switch error

DTC - 70 A/C pressure sensor circuit error (high pressure indicated)

DTC - 71 A/C evaporator temp sensor circuit error (low temp indicated)

DTC - 72 VSS signal circuit error

DTC - 73 A/C evaporator temp sensor circuit error (high temp indicated)

DTC - 75 Digital EGR solenoid #1 circuit error

DTC - 76 Digital EGR solenoid #2 circuit error

DTC - 77 Digital EGR solenoid #3 circuit error

DTC - 79 Transmission fluid overtemp

DTC - 80 Transmission component slipping

DTC - 82 3x Crankshaft position sensor circuit error

DTC - 85 PROM error

DTC - 86 A/D error

DTC - 87 EEPROM error (flash memory error)

DTC - 90 TCC error

DTC - 93 Transmission pressure control solenoid circuit error

DTC - 96 Transmission system voltage low

DTC - 98 Invalid PCM program

DTC - 99 Invalid PCM program

[68 TT]

Originally Posted by BLE 'BURBAN

When doing this, DO NOT START THE VEHICLE!!!

Each code will flash 3 times before moving on to the next code.
First and last code to flash will be code 12 which will be *(pause)** (long pause) *(pause)** (long pause) *(pause)**
a bit of a longer pause will happen before the next trouble code will flash, again 3 times. Once all trouble codes have flashed it will flash code 12 again.

If it doesn't flash a code 12 then the ECM / PCM does not self check good and you need another one.

I had one where the circuit board broke free of the case and was in limp home mode that wouldn't flash a code 12.

[iroc12valve]

Thanks You
do you happen to know where to find out what the codes correspond to (other than in those chilton manuals i cant find mine right now)

[63chevyll]

if you post the codes we can help you out,

ill be outa town this weekend, but post them anyway

[iroc12valve]

The internet really is a valuable tool, Thank you very much
I nominate this thread for a sticky so that these codes/procedures will be easily located by all

[BGRAFX]

I tried the paperclip method on my 91burb and couldn't figure it out so I went to the auto parts store and they will do diagnostics test for free.

[Keith Seymore]

Good info, guys.

Do I also understand correctly that you can't do this on a '96 and up vehicle (specifically a '97 Suburban) because of more stringent OBD requirements?

K

[BGRAFX]

Correct if I'm wrong but I think it only works on OBD1 plugs as the 95 and newer trucks have a completely different plug OBD2

[BGRAFX]

Here is a website for obd-codes http://www.obd-codes.com/faq/read-gm...codes-free.php

[63chevyll]

paper clip only on 95 AND OLDER, 96 and newer needs a scanner