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Retrieving and Deciphering GM Computer Command Control Trouble Codes.

Retrieving Computer Command Control Trouble Codes
Assembly Line Diagnostic Link (ALDL)location:


1981 Model Procedure:
If you have the distinct honor of having one of the first Computer Command Control (CCC) systems put into an El Camino, use this method. I think it was first introduced in California in 80 and the rest of the U.S. got it in 81. The 80/81 CCC system is different from all other 5th Generation El Camino CCC systems.


This is the 1981 Assembly Line Diagnostic Link (ALDL)

In order to pull the stored codes do this:

1. With the ignition off, jumper the two far right terminals as shown in the picture. "D" is the diagnostic terminal and "E" is ground.
2. Turn on the ignition but do not start the engine.
3. The SES light will begin to flash a Trouble code 12. One flash, a short pause, and two flashes. There will be a longer pause and the Code 12 will repeat two more times.
4. The stored Trouble Codes will now flash. Each Code will be repeated three times. Write them down.
5. When Code 12 flashes again that indicates that there are no more stored Trouble Codes.​
Diagnostic trouble codes may be cleared by disconnecting the battery, or removing the ECM fuse for at least 20 seconds. Reconnect and recheck codes to confirm the repair.​
Ernie G.
87ElCamino
1982 And Later Model Procedure:

  • Turn ignition switch to OFF position
  • Locate Data Link Connector (ALDL).
  • Jumper the A&B terminals using a paper clip or a jumper wire.
  • Turn Ignition switch to ON position.
  • Count the flashes on the "CHECK ENGINE" or "SERVICE ENGINE" light.
  • FLASH, pause, FLASH, FLASH = code 12


Diagnostic trouble codes may be cleared by disconnecting the battery, or removing the ECM fuse for at least 20 seconds. Reconnect and recheck codes to confirm the repair.

<table bgcolor="#ffffff" border="1" bordercolor="#669999" cellpadding="7" cellspacing="1" height="1157" width="98%"> <tbody> <tr> <td height="30" valign="top" width="11%"> Code
</td> <td height="30" valign="top" width="19%"> Circuit</td> <td height="30" valign="top" width="74%"> Possible Causes/Solutions
</td></tr> <tr> <td height="41" valign="top" width="11%">12
</td> <td height="41" valign="top" width="19%"> Diagnostics Entered</td> <td height="41" valign="top" width="74%">Normal code with ignition on and engine off. Indicates no distributor reference pulse to ECM. Not stored in memory.
</td></tr> <tr> <td height="32" valign="top" width="11%">13
</td> <td height="32" valign="top" width="19%">Oxygen sensor circuit
</td> <td height="32" valign="top" width="74%">Check for a sticking or maladjusted throttle position sensor. Check the wiring and connectors from the oxygen sensor. Replace the oxygen sensor.
</td></tr> <tr> <td height="48" valign="top" width="11%">14
</td> <td height="48" valign="top" width="19%">Coolant sensor/high temp
</td> <td height="48" valign="top" width="74%">If the engine is experiencing overheating problems the problem must be rectified before continuing. Check all wiring and connectors associated with the coolant temperature sensor. Replace the coolant temperature sensor.
</td></tr> <tr> <td height="32" valign="top" width="11%">15
</td> <td height="32" valign="top" width="19%">Coolant sensor/low temp
</td> <td height="32" valign="top" width="74%">See above, then check the wiring connections at the ECM.
</td></tr> <tr> <td height="32" valign="top" width="11%">21
</td> <td height="32" valign="top" width="19%">Throttle position sensor/high
</td> <td height="32" valign="top" width="74%">Check for a sticking or maladjusted TPS plunger. Check all wiring and connections between the TPS and the ECM. Adjust or replace the TPS.
</td></tr> <tr> <td height="32" valign="top" width="11%">22
</td> <td height="32" valign="top" width="19%">Throttle position sensor/low
</td> <td height="32" valign="top" width="74%">Check the TPS adjustment. Check the ECM connector. Replace the TPS.
</td></tr> <tr> <td height="32" valign="top" width="11%">23
</td> <td height="32" valign="top" width="19%">Mixture control solenoid
</td> <td height="32" valign="top" width="74%">The mixture control solenoid is open or grounded.
</td></tr> <tr> <td height="48" valign="top" width="11%">24
</td> <td height="48" valign="top" width="19%">Mixture control solenoid
</td> <td height="48" valign="top" width="74%">A fault in this circuit should be indicated only when the vehicle is in motion. Disregard Code 24 if it is set when the drive wheels are not turning. Check the connections at the ECM. Check the TPS setting.
</td></tr> <tr> <td height="16" valign="top" width="11%">32
</td> <td height="16" valign="top" width="19%">BARO circuit low
</td> <td height="16" valign="top" width="74%">Barometric pressure sensor circuit is low.
</td></tr> <tr> <td height="32" valign="top" width="11%">33
</td> <td height="32" valign="top" width="19%">MAP sensor
</td> <td height="32" valign="top" width="74%">Check the vacuum hoses from the MAP sensor. Check the electrical connections at the ECM. Replace MAP sensor.
</td></tr> <tr> <td height="48" valign="top" width="11%">34
</td> <td height="48" valign="top" width="19%">Vacuum sensor or MAP sensor
</td> <td height="48" valign="top" width="74%">Code 34 will set when the signal voltage from the MAP sensor is too low. Instead the ECM will substitute a fixed MAP value and use the TPS to control fuel delivery. Replace the MAP Sensor.
</td></tr> <tr> <td height="16" valign="top" width="11%">35
</td> <td height="16" valign="top" width="19%">ISC valve
</td> <td height="16" valign="top" width="74%">Idle Speed Control error. Replace the ISC.
</td></tr> <tr> <td height="16" valign="top" width="11%">41
</td> <td height="16" valign="top" width="19%">EST circuit
</td> <td height="16" valign="top" width="74%">No distributor reference pulses to the ECM at specified engine vacuum.
</td></tr> <tr> <td height="32" valign="top" width="11%">42
</td> <td height="32" valign="top" width="19%">Electronic Spark Timing
</td> <td height="32" valign="top" width="74%">Electronic Spark Timing bypass circuit or EST circuit is grounded or open. A bad HEI module can cause this code.
</td></tr> <tr> <td height="32" valign="top" width="11%">43
</td> <td height="32" valign="top" width="19%">Electronic spark control unit
</td> <td height="32" valign="top" width="74%">The ESC retard signal has been on for too long or the system has failed a functional check.
</td></tr> <tr> <td height="48" valign="top" width="11%">44
</td> <td height="48" valign="top" width="19%">Lean exhaust
</td> <td height="48" valign="top" width="74%">Check the ECM wiring connections. Check for vacuum leakage at the carburetor base gasket, vacuum hoses or the intake manifold gasket. Replace the oxygen sensor.
</td></tr> <tr> <td height="32" valign="top" width="11%">45
</td> <td height="32" valign="top" width="19%">Rich exhaust
</td> <td height="32" valign="top" width="74%">Check the evaporative charcoal canister and its components for the presence of fuel. Replace the oxygen sensor.
</td></tr> <tr> <td height="32" valign="top" width="11%">51
</td> <td height="32" valign="top" width="19%">PROM or MEM-CAL
</td> <td height="32" valign="top" width="74%">Make sure that the PROM and/or MEM-CAL is properly installed in the ECM. Replace the PROM and/or MEM-CAL.
</td></tr> <tr> <td height="16" valign="top" width="11%">52
</td> <td height="16" valign="top" width="19%">CALPAK
</td> <td height="16" valign="top" width="74%">Check the CALPAK to insure proper installation. Replace the CALPAK.
</td></tr> <tr> <td height="32" valign="top" width="11%">53
</td> <td height="32" valign="top" width="19%">EGR valve
</td> <td height="32" valign="top" width="74%">Exhaust Gas Recirculation valve vacuum sensor has received improper EGR vacuum.
</td></tr> <tr> <td height="32" valign="top" width="11%">54
</td> <td height="32" valign="top" width="19%">M/C solenoid
</td> <td height="32" valign="top" width="74%">The mixture control solenoid voltage is high at the ECM because of a shorted M/C solenoid circuit and/or faulty ECM.
</td></tr> <tr> <td height="32" valign="top" width="11%">55
</td> <td height="32" valign="top" width="19%">ECM
</td> <td height="32" valign="top" width="74%">Be sure that the ECM ground connections are tight. If they are, replace the ECM.
</td></tr></tbody></table>



Diagnostic trouble codes may be cleared by disconnecting the battery, or removing the ECM fuse for at least 20 seconds. Reconnect and recheck codes to confirm the repair.
Information compiled by Ernie G. and Robert More
 

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Update NOTE!

Code #24 Circuit should read Vehicle Speed Sensor instead of Mixture Control Solenoid.

Thanks to JJLT1
 
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