Assembly Line Data Link (ALDL) Information
By: Jared Burkardt
- Paper Clip
ALDL Terminal Identification
|A -- Ground||G -- Fuel Pump|
|B -- Diagnostic Terminal||H -- Brake Sense Speed Input|
|F -- TCC||M -- Serial Data (special tool needed - Do Not Use)|
- Engine Diagnostics - Terminals (A) and (B).
- To Engage the Transmission Converter Clutch (TCC) - Terminals (A) and (F).
- To Engage the Fuel Pump - Connect a fused (+) lead to Terminal (G).
- Brake Diagnostics - Terminals (A) and (H).
- (M) is a Serial Data Connection for 4 Cyl? engines and needs a special tool - Do Not USE!
Engine Diagnostic Codes:
To do a diagnostic on engine codes you take a paper clip and connect terminal (A) and (B) together. A Code 12 will flash on the Check Engine light 3 times first and then give you any additional codes if present. A code is displayed for example 12 (1 flash, pause, 2 flashes). Listed below is a list of all the available codes and what they mean.
|Trouble Codes||Circuit or System||Probable Cause|
|Code 12||No distributor
pulses to the ECM
|This code will flash whenever the diagnostic terminal is grounded with the ignition turned On and the engine not running. If additional trouble codes are stored in the ECM then they will appear after this code has flashed 3 times. If this code appears while the engine is running, no reference pulses from the distributor are reaching the ECM.|
|Code 13||Oxygen sensor circuit||Check for a sticking or misadjusted throttle position sensor. Check the wiring and connectors from the oxygen sensor. Replace the oxygen sensor.|
|Code 14||Coolant sensor/High temp||If the engine is experiencing overheating problems the problem must be rectified before continuing. Check all wiring and connector associated with the coolant temperature sensor. Replace the coolant temperature sensor.|
|Code 15||Coolant sensor/Low temp||See Above, then check the wiring connections at the ECM.|
|Code 21||Throttle position
|Check for a sticking or misadjusted TPS plunger. Check all wiring and connections between the TPS and the ECM. Adjust or replace the TPS. (see other instructions on doing this)|
|Code 22||Throttle position
|Check TPS adjustment. Check the ECM connector. Replace the TPS.|
|Code 23||MAT low temp indication||Sets if the Manifold Air Temperature (MAT) sensor, connections or wires are open for 3 seconds.|
|Code 24||Vehicle speed sensor||A fault in this circuit should be indicated only when the vehicle is in motion. Disregard if it is set when the drive wheels are not turning. Check the connections at the ECM. Check the TPS setting.|
|Code 25||ATI sensor/high air||High temperature indication. Sets if the sensor or signal line becomes grounded for 3 seconds.|
|Code 31||Wastegate Overboost|
|Code 32||EGR||Vacuum switch shortened to ground on start-up, switch not closed after the ECM has commanded the EGR for a specified period of time or the EGR solenoid circuit is open for a specified period of time. Replace the EGR valve.|
|Code 33||MAP sensor||Check the vacuum hoses from the MAP sensor. Check the electrical connections at the ECM. Replace MAP sensor.|
|Code 34||Vacuum sensor or
|This 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.|
|Code 35||IAC valve||Idle Air Control error. Code will set when closed throttle speed is 50 rpm above or below the correct idle speed for 30 seconds. Replace the IAC.|
|Code 42||Electronic Spark
|This code is when this circuit is grounded or open. A malfunctioning HEI module can cause this code.|
|Code 43||Electronic Spark
|The ESC retard signal has been on for too long or the system has failed a functional check.|
|Code 44||O2/Lean exhaust||Check the ECM wiring connections, particularly terminals 8 and 15. Check for vacuum leakage at the TBI base gasket, vacuum hoses or the intake manifold gasket. Replace the oxygen sensor.|
|Code 45||O2/Rich exhaust||Check the evaporative charcoal canister and its components for the presence of fuel. Replace the oxygen sensor.|
|Code 51||PROM or MEM-CAL||Make sure the PROM or MEM-CAL is properly installed in the ECM. Replace the PROM or MEM-CAL.|
|Code 52||CALPAK||Check the CALPAK to insure proper installation. Replace the CALPAK.|
|Code 53||System over-voltage (indicates a basic alternator problem)||Check charging system.|
|Code 54||Fuel Pump||Low fuel pump voltage. Sets when the fuel pump voltage is less than 2 volts when reference pulses are being received.|
|Code 55||ECM||Be sure that the ECM ground connections are tight. If they are, replace the ECM.|
4-Wheel Anti-Lock Diagnostic Codes:
To do a diagnostic on 4WAL codes you take a paper clip and connect terminal (A) and (H) together. After 20 seconds if any codes are present they will be displayed by the flashing of the Anti-Lock light. A code is displayed for example 12 (1 flash, pause, 2 flashes). Listed below is a list of all the available codes and what they mean.
To clear the code from the ECU memory, with the ignition On, place the jumper between (A) and (H) for two seconds, remove for one second, and replace again for two seconds. The Antilock/Brake light should light, then go off.
Note: How Codes 86 and 88 work if the problem exist, I don't know, I am just passing the info from the manual.
|Trouble Codes||Circuit or System||Probable Cause|
|Code 21||Right Front Wheel Circuit||Faulty wheel sensor or open circuit.|
|Code 22||Right Front Wheel Circuit||No signal. Remove the wheel. Check for a damaged sensor or loose electrical connectors.|
|Code 23||Right Front Wheel Circuit||Intermittent signal, indicating a loose electrical connector.|
|Code 25||Left Front Wheel Circuit||No signal. Remove the wheel. Check for a damaged sensor or loose electrical connectors.|
|Code 26||Left Front Wheel Circuit||Intermittent signal, indicating a loose electrical connector.|
|Code 27||Left Front Speed Sensor Circuit||Faulty sensor or loose electrical connector.|
|Code 28||Speed Sensor Signal||Erratic brake action at low speeds and pedal pressures indicates a fault in the speed sensor circuit or speedometer.|
|Code 29||EHCU Circuit||A loss of signal from all four sensors indicates a loose EHCU connector.|
|Code 31||Right Rear Speed Sensor Circuit||An intermittent code indicates a loose electrical connector.|
|Code 32||Right Rear Wheel Circuit||No signal. Remove the wheel. Check for a damaged sensor or loose electrical connectors.|
|Code 33||Right Rear Wheel Circuit||Intermittent signal, indicating a loose electrical connector.|
|Code 35||Left Rear Wheel Circuit||Intermittent signal, indicating a loose electrical connector.|
|Code 36||Left Rear Speed Sensor Circuit||No signal. Remove the wheel. Check for a damaged sensor or loose electrical connectors.|
|Code 37||Left Rear Speed Sensor Circuit||An inconsistent anti-lock action at low speeds and pedal pressure is a sign of a fault in the speed sensor unit or connectors.|
|Code 38||EHCU valve circuit||A pulsing pedal indicates a defective wheel sensor or faulty EHCU valve.|
|Code 41 through 66||4WAL control unit or motor circuit||Check for a loose ground connection at the motor circuit. Clear the code and drive the vehicle. If any of these codes return, the EHCU valve may be faulty.|
|Code 67||Motor circuit||Check the motor for loose electrical connections.|
|Code 68||Motor circuit||A locked motor or an open circuit. Check the motor for loose electrical connections.|
|Code 71 through 74||4WAL control unit||Clear the code and drive the vehicle. If any of these codes return, the EHCU valve may be faulty.|
|Code 81||Brake switch circuit||Make sure the driver hasn't been riding the brake. Check the brake switch adjustment and electrical connections|
|Code 86||Anti-Lock warning light||Check the light and wiring for a short circuit.|
|Code 88||Brake warning light||Check the light and wiring for a short circuit.|