Error codes

Is it possible to read 91 Caprice error codes somehow without any code readers? Chrysler cars blink them with LED on dashboard, can GM do something similar? thanks.

Right, thats what the code reader does. It does not actually have a display (older ones don't, new ones may), but it shorts certain terminals on the Assembly Line Diagnostics (ALD) port to cause the codes to be displayed on the dash. The service engine soon light will flash a certain number of times and these will be of a certain duration to identify the number and place value (2 long flashes followed by four short flashes is 24). You can so do that with a home made jumper but I'm not sure which ports you need to short. Some of the guys on this forum should be able to tell you that.

thanks. Im glad to hear that. Im from Czech republic, where is problem to order some code reader GM compatible from US.

Tools needed:
Your car keys
A paper clip or a three(3) inch long piece of safety wire.

First thing you need to do is find your Assembly Line Diagnostic Link or ALDL. It s small black plastic piece about two (2) inches wide by one half(0.5) inch tall. It has twelve (12) female connector inside. The ALDL can be found under the driver's side of the dash, usually attached with two (2) screws to the bottom side of the dash.

The ALDL :

Now that you've found the ALDL, bend the paper clip or the piece of wire into a U shape. With the ignition in the OFF position. Insert one end into the A slot and one into the B slot. Now turn the the ignition to the ON position. DO NOT start the car. As the ECM begins it's self-test if will begin to flash the SES light to provide the codes. The flashes will appear like this : *flash* short pause *flash* *flash* long pause then repeat. Each code will be displayed three(3) times. Code 12 will be repeated to indicate the end of the set codes. If you all you get is Code 12 then you have no codes set in your ECM.

An example of a sequence for a common code :
*flash* short pause *flash* *flash* long pause = Code 12, Testing the ECM
*flash* short pause *flash* *flash* long pause = Code 12, Testing the ECM
*flash* short pause *flash* *flash* long pause = Code 12, Testing the ECM
*flash* *flash* *flash* short pause *flash* *flash* long pause = Code 32, EGR
*flash* *flash* *flash* short pause *flash* *flash* long pause = Code 32, EGR
*flash* *flash* *flash* short pause *flash* *flash* long pause = Code 32, EGR
*flash* short pause *flash* *flash* long pause = Code 12, Testing the ECM
*flash* short pause *flash* *flash* long pause = Code 12, Testing the ECM
*flash* short pause *flash* *flash* long pause = Code 12, Testing the ECM


Clearing the codes is really quite easy. Unhook your battery for about 2-3 minutes and then hook it back up.

These codes cover the OBD-I computers only.....
All currently listed codes are from the 1989 B-car Service Manual. Why? Because that's what I have. If you have others that aren't listed or need to be added, just let me know.


CODE AND CIRCUIT POSSIBLE CAUSE

CODE 12 = System check
Indicates that the ECM is functioning.

CODE 12 = No Engine Speed Reference - VIN 'Y' CARB
Indicates an open or ground in the distributor reference circuit.

CODE 13 = OPEN Oxygen Sensor (O2)
Indicates that the oxygen sensor circuit circuit or sensor was open for one minute while off idle.

CODE 14 = Coolant Sensor (CTS)
Sets if the sensor or signal line are grounded for 3 seconds. HIGH Temperature indication.

CODE 15 = Coolant Sensor (CTS)
Sets if the sensor wires or connections are open for 3 seconds. LOW Temperature indication.

CODE 21 = Throttle Position Sensor (TPS)
TPS voltage of more than 2.5 volts for 3 seconds at an engine speed less than 1200 rpm. HIGH Voltage Signal.

CODE 22 = Throttle Position Sensor (TPS)
A shorted to ground or open signal circuit will set code in 3 seconds. LOW Voltage Signal.

CODE 23 = Manifold Air Temperature Sensor (MAT)
Sets if the sensor wires or connections are open for 3 seconds or Intake Air Temperature (IAT) LOW Temperature indication.

CODE 24 = Vehicle Speed Sensor (VSS)
No vehicle speed present during road/load deceleration. NO Vehicle Speed Indication.

CODE 25 = Manifold Air Temperature Sensor (MAT)
Sets if the sensor or signal line are grounded for 3 seconds. Or Intake Air Temperature (IAT)
HIGH Temperature indication.

CODE 32 = Exhaust Gas Recirculation (EGR)
OR Vacuum switch shorted to ground on start up. Switch not closed after the ECM has commanded EGR for a specified period of time OR EGR solenoid circuit open for a specified period of time.

CODE 33 = Manifold Absolute Pressure (MAP)
MAP sensor output too high for 5 seconds or an open circuit. LOW Vacuum.

CODE 34 = Manifold Absolute Pressure (MAP)
Low or no output from sensor with engine running. HIGH Vacuum.
CODE 35 = Idle Air Control (IAC)
IAC error.

CODE 42 = Electronic Spark Timing (EST)
ECM has seen an open or grounded EST or Bypass circuit.

CODE 43 = Electronic Spark Control (ESC)
Signal to the ECM has remained low for too long or the system has failed a functional check.

CODE 44 = LEAN Exhaust Indication
If voltage to oxygen sensor remains BELOW .2v for more than 20 seconds code is set.

CODE 45 = RICH Exhaust Indication
If voltage to oxygen sensor remains ABOVE .7v for more than 1 minute code is set.

CODE 51 = PROM - Faulty MEM-CAL or ECM.

CODE 52 = Faulty or missing CAL-PACK.

CODE 53 = System overvoltage
Indication of a faulty alternator or regulator. Camaro/Firebird uses a Code 53 for Vehicle Anti-Theft System (VATS).

CODE 54 = Low Voltage To Fuel Pump
Sets when the fuel pump voltage is less than 2 volts when reference pulses are being received.

CODE 55 = Faulty ECM

thank you very very much. I will try this.

So I did :) These codes I got.

CODE 43 = Electronic Spark Control (ESC)
Signal to the ECM has remained low for too long or the system has failed a functional check.

CODE 44 = LEAN Exhaust Indication
If voltage to oxygen sensor remains BELOW .2v for more than 20 seconds code is set.

CODE 45 = RICH Exhaust Indication
If voltage to oxygen sensor remains ABOVE .7v for more than 1 minute code is set.

I cant imagine what does mean, byt I have two theories. First is, that fuel injection have problems with getting right level of air to mix it with fuel. Second is that exhaust gas oxygen sensor might be damaged.

What 43 means I totally dont know.

43 = Knock sensor usually. Follow the wire to it on the passenger side of the block. Make sure it's fine.

You are on the right track as far as the A/F ration being out of whack based on the other two codes. I'd start by replacing the Oxygen sensor and see how that effects those two codes.

thanks. Btw. trying is hard for me. I must order every part form US, price get higher for transport. I hope it will be this. :)

An o2 code may be something as simple as fuel filter. I'd check that before shelling out $$$ for an o2 sensor.

JS