Do you have a code reader? No? Well, you do not need one for we will show you how to retrieve codes for the price of a paperclip (literally) and will also provide you with what the trouble codes stand for. Remember, we cannot diagnose your vehicle for you - we are supplying you with information that you can use as a Tool. Yeh, we can be good like that. Read on....
Retrieving the Codes
1) Find the ALDL terminal.
This is attached to the bottom left side of the dashboard facing outwards towards the seat. It's easiest to see standing just outside of the driver's door with the driver's door being opened, of course. It is identifiable by being - rectangular in shape, a female socket, and having two rows of 6 (12 total) terminals.
Each terminal has a corresponding letter assigned to it as shown in below table.
2) Check for codes.
With the engine off and the ignition key turned to the 'Run' position insert a paper clip or small jumper wire into terminal's A and B - the top two furthest to the right. See table above.
The check engine light will start to blink. The first code will be 12 - one flash of the check engine light followed by a short pause and then two quicker flashes of the check engine light. How do we know you'll have this code? All vehicle's with a working Check Engine Light will have this code! It is a diagnostic test to make sure the light is working. If there is no blinking light - the light does not work.
All codes will be shown 3 times in a row before the next code (if there are any) will appear. How do you know when all the codes have been shown? Code 12 will be shown again. The codes will keep cycling until the "jumper" is removed from the A+B terminals.
If you have not retrieved codes this way before do not become embarrassed if the flashing Check Engine Light leaves you a little mixed up - it's kind of like Morse Code but in a much easier way. If you get confused you can re-start the whole process by removing and then re-installing the jumper. You'll catch on within a few minutes of doing this.
3) What do the codes stand for?
Trouble Code |
SYSTEM |
Indicating |
12 |
Diagnostic |
Checking for operation of CEL bulb |
| 13 |
Oxygen Sensor Circuit |
No signal to computer |
| 14 |
Coolant Sensor Circuit |
Excessive HIGH temperature indicated |
| 15 |
Coolant Sensor Circuit |
Excessive Low temperature indicated |
| 16 |
VSS - Vehicle Speed Sensor |
Signal Loss |
| 21 |
TPS - Throttle Position Switch |
High Signal Voltage |
| 22 |
TPS |
Low Signal Voltage |
| 24 |
VSS |
Set when in motion only - disregard if set in park |
| 32 |
EGR |
EGR system failure |
| 33 |
MAP - manifold absolute pressure sensor |
MAP sensor voltage high |
| 34 |
MAP |
MAP sensor voltage low |
| 35 |
IAC - Idle Air Control Motor |
Idle speed above/below desired idle speed |
| 36 |
Idle Speed Control Actuator |
Open or Short Circuit |
| 42 |
Ignition Control |
open/short/component failure |
| 43 |
ESC - electronic spark control |
ESC module not receiving knock sensor signal |
| 44 |
Lean Exhaust |
Low oxygen sensor voltage |
| 45 |
Rich Exhaust |
High oxygen sensor voltage |
| 51 |
PROM (Memcal) |
Faulty computer chip |
| 53 |
System voltage high |
Carging System is over 17.1 volts |
| 54 |
Fuel pump relay |
Low voltage / short |
| 55 |
ECM |
Computer (ECM) failure |
| The Following only apply to 1994 + |
| 28 |
Transmission range pressure |
open in one of these pressure switches |
| 37 |
Brake Switch |
brake switch stuck ON |
| 38 |
Brake Switch |
Brake Switch stuck OFF |
| 39 |
Torque Converter |
TC clutch solenoid stuck OFF |
| 52 |
System Voltage High |
ignition feed voltage over 16 volts |
To be continued....... |
