Trouble Codes

Circuit or System

Probable Cause


Code 12

(1 Flash, Pause, 2 Flashes)

No distributor reference pulses to ECM (Electronic Control Module)

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 they will appear after this code has flashed three
times. If this code appears while the engine is running, no reference pulses
from the distributor are reaching the ECM (Electric Control Module)




Code 13

(1 flash, pause, 3 flashes)

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

(1 flash, pause, 1 flash)



Coolant sensor/low temperature

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.


Code 15

(1 flash, pause, 5 flashes)

Coolant sensor low temperature

See above, then check the wiring connections at the ECM (Electric Control
Module)


Code 21

(2 flashes, pause, 1 flash)

Throttle position sensor/voltage high

Check for sticking or misadjusted TPS (Throttle position sensor) plunger.
Check all wiring and connections between the TPS and the ECM. Adjust or
replace the TPS.


Code 22

(2 flashes, pause, 2 flashes)

Throttle position sensor/voltage low

Check the TPS adjustment. Check the ECM connector. Replace the TPS.




Code 24

(2 flashes, pause, 4 flashes)

Vehicle speed sensor

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.


Code 32 (fuel injected)

(3 flashes, pause, 2 flashes)

EGR (Exhaust Gas Recirculation)

Vacuum switch shorted 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 specified period of time. Replace the EGR valve.


Code 33

(3 flashes, pause, 3 flashes)

MAP sensor

Check the vacuum hoses from the MAP sensor. Check the electrical connections
at the ECM. Replace the MAP sensor.


Code 34

(3 flashes, pause, 4 flashes)

Vacuum sensor or MAP sensor. Replace the MAP sensor.

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.

Trouble Codes Continued.


Code 41

(4 flashes, pause, 1 flash)

EST (Electronic Spark Timing) circuit

No distributor reference pulses to the ECM at specified engine vacuum.


Code 42

(4 flashes, pause, 2 flashes)

Electronic Spark Timing

Electronic Spark Timing bypass circuit or EST (Electronic Spark Timing)
circuit is grounded or open. A malfunctioning HEI (High Energy Ignition)
module can cause this code.


Code 43

(4 flashes, pause, 3 flashes)

ESC (Electronic spark control) unit

The ESC (Electronic spark control) retard signal has been on for too long or
the system has failed a functional check.


Code 44

(4 flashes, pause, 4 flashes)

Lean exhaust

Check the ECM wiring connections, particularly terminals 15 and B. Check for
vacuum leakage at the TBI base gasket, vacuum hoses or the intake manifold
gasket. Replace the oxygen sensor.


Code 45

(4 flashes, pause, 5 flashes)

Rich exhaust

Check the evaporative charcoal canister and its components for the presence
of fuel. Replace the oxygen sensor.


Code 51

(5 flashes, pause, 1 flash)

PROM or MEM-CAL

Make sure that the PROM or MEM-CAL is properly installed in the ECM. Replace
the PROM or MEM-CAL.


Code 52

(5 flashes, pause, 2 flashes)

CALPAK

Check the CALPAK to insure proper installation. Replace the CALPAK.


Code 54 (fuel injected)

(5 flashes, pause, 4 flashes)

Fuel pump

Low fuel pumps voltage. Sets when the fuel pump voltage is less than 2 volts
when reference rules are being received.


Code 55

(5 flashes, pause, 5 flashes)

ECM

Be sure that the ECM ground connections are tight. If they are replace the
ECM.




How to read the ECM codes.








Push one end of a jumper in to "TEST" and the other end in to "GND". Use
paperclip.

Turn the ignition to the On position (NOT THE START POSITION).

If "Service Engine Soon" light flash Trouble code 12, then system is
working.

If no codes have been stored, Trouble code 12 will continue flashing

Until the jumper is removed. All Trouble codes will flash three times.

To clear the Trouble code(s) from the ECM memory, unplug the battery cable.

 

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