Digit 1. Country 1 - United States
2 - Canada
J - Japan 2. Manufacturer G - General Motors 3. Division 1 - Chevrolet 4. Car line code G - El Camino/Monte Carlo
A - Celebrity B - Impala/Caprice (RWD)
F - Camaro
J - Cavalier
M - Sprint
R - Spectrum
S - Nova
T - Chevette
X - Citation
Y - Corvette 5. Series Z - Monte Carlo
B - Chevette
C - Cavalier
D - Cavalier CS
E - Cavalier Hatchback/Type 10
F - Spectrum (Level I)
G - Spectrum (Level II)
H - Citation Coupe
J - Chevette Scooter
K - Nova
L - Impala
N - Caprice Classic
P - Camaro Sport Coupe
R - Sprint
S - Camaro Berlinetta
W - Celebrity
X - Citation/Malibu Classic
Y - Corvette 6+7. Body Style 11 - 2 Door Notch back Coupe
08 - 2 Door Hatchback
19 - 4 Door Notch back Sedan
27 - 2 Door Notch back Coupe
35 - Station Wagon
37 - 2 Door Notch back Coupe
67 - 2 Door Convertible
68 - 4 Door Sedan Hatchback
69 - 4 Door Sedan Notch back
77 - 2 Door Hatchback Coupe
80 - El Camino - 2 Door Pickup Delivery
87 - 2 Door Plain back Coupe 8. Engine G - 305 (5.0L) 4 BBL. Hi Output
2 - 151 (2.5L) TBI / Electronic Fuel Injection
5 - 97 (1.5L) Diesel
6 - 350 (5.7L) 4 BBL.
8 - 350 (5.7L) Electronic Fuel Injection
A - 231 (3.8L) 2 BBL.
C - 98 (1.6L) 2 BBL.
D - 111 (1.8L) Diesel
F - 305 (5.0L) 4 BBL.
H - 305 (5.0L) 4 BBL.
K - 229 (3.8L) 2 BBL.
M - 61 (1.0L) BBL.
N - 350 (5.7L) Diesel
P - 121 (2.0L) TBI / Electronic Fuel Injection
R - 151 (2.5L) TBI / Electronic Fuel Injection
S - 173 (2.8L) Electronic Fuel Injection
T - 260 (4.3L) Diesel
V - 260 (4.3L) Diesel
W - 173 (2.8L) Multi-port Fuel Injection Hi Output
X - 173 (2.8L) 2 BBL.
Z - 173 (2.8L) 2 BBL Hi Output / 260 (4.3L) TBI 9. Check Digit IGNORE 10. Year F - 1985
G - 1986
H - 1987
J - 1988 11. Production Plant R - Arlington, TX
1 - Oshawa, ONT
2 - Moraine, OH / St. Therese, PA
3 - Detroit, MI / St. Eustacle, PA
4 - Orion, MI / Scarborough, ONT
5 - Bowling Green, KY / London, ONT
6 - Oklahoma City, OK
7 - Lordstown, OH
8 - Shreveport, LA / Fujisawa, JAP
A - Lakewood, GA
B - Baltimore, MD
C - South Gate, CA
D - Doraville, GA
E - Linden, NJ
F - Flint, MI
G - Framingham, MA
H - Flint, MI
J - Janesville, WI
K - Leeds, MO
L - Van Nuys, CA
N - Norwood, OH
P - Pontiac, MI
S - St. Louis, MO
T - Tarrytown, NY
W - Willow Run, MI
X - Fairfax, KS
Y - Wilmington, DE
Z - Fremont, CA 12-17 Sequential Build
Trouble codes Circuit or system Probable cause Code 12
(1 flash, pause, 2 flashes)
No distributor reference pulses to 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 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. 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, 4 flashes)
Coolant sensor/high temp 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 temp See above, then check the wiring connections
at the ECM. Code 21
(2 flashes, pause, 1 flash)
Throttle position sensor/voltage high Check for a sticking or misadjusted TPS 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 23 (carbureted)
(2 flashes, pause, 3 flashes)
Mixture control solenoid The mixture control solenoid is open or grounded. 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 (carbureted)
(3 flashes, pause, 2 flashes)
BARO circuit low Barometric pressure sensor circuit low. Code 32 (fuel injected)
(3 flashes, pause, 2 flashes)
EGR 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 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. Code 35 (carbureted)
(3 flashes. pause, 5 flashes)
ISC valve Idle Speed Control error. Replace the ISC. Code 41
(4 flashes, pause, 1 flash)
EST 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
circuit is grounded or open. A malfunctioning HEI module can cause this
code. Code 43
(4 flashes, pause, 3 flashes)
Electronic spark control unit The ESC 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 53 (carbureted)
(5 flashes, pause, 3 flashes)
EGR valve Exhaust Gas Recirculation valve vacuum sensor
has received improper EGR vacuum. Code 54 (carbureted)
(5 flashes, pause, 4 flashes)
M/C solenoid The mixture control solenoid voltage is high
at the ECM because of a shorted M/C solenoid circuit and/or faulty ECM. Code 54 (fuel injected)
(5 flashes, pause, 4 flashes)
Fuel pump Low fuel pump voltage. Sets when the fuel pump
voltage is less than 2 volts when reference pules 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.