The ATGO ECM Code Page will help you find the problem associated with your ECM Trouble Codes. Check your Trouble Codes using the instructions below and then compair the code to the correct chart below.
- Turn ignition switch to OFF position
- Locate Data Link Connector (DLC), see image above, Blue A and Red B.
- Jumper the A&B terminals(a paper clip or a jumper wire work ok)
- Turn Ignition switch to ON position.
- Count the flashes on the “CHECK ENGINE“or “SERVICE ENGINE” light.
- FLASH, pause, FLASH, FLASH = code 12
To clear all codes from your ECM, disconnect the negative battery cable at the battery and wait about 30 seconds then reconnect it. If your cars stereo requires you to enter a 4 digit code when you do this, the best thing for you to do is to just remove the fuse going to the ECM.
Select your motor:
2.5L Carb 2.5L TBI 2.8L Carb 2.8L MFI 3.1L MFI 5.0L/5.7L Carb 5.0L TBI 5.0L/5.7L TPI
13 Oxygen sensor circuit 14 Coolant temperature sensor voltage low 15 Coolant temperature sensor voltage high 21 TPS voltage was above 2.5 volts for 10 seconds when the MAP sensor signal showed manifold vacuum to be 15 pounds or more with an engine speed less than 1300 RPM. 22 TPS voltage was under 0.2 volts for 4 seconds when the engine was running. 24 Vehicle Speed sensor circuit 33 MAP sensor signal voltage was too high (low vacuum) for 5 seconds when throttle opening was under 2%. 42 The EST signal did not change when the ECM applied bypass voltage to the ignition module. 44 Oxygen sensor lean exhaust indication. 45 Oxygen sensor rich exhaust indication. 51 PROM not reading. 55 ECM problem
13 Oxygen sensor voltage stays between 0.35 and 0.55 volts for 3 seconds during closed loop operation and will set code after 40 seconds for Century and Cutlass Ciera. For the Lumina, the oxygen sensor voltage stays between 0.35 and 0.55 volts for 60 seconds during closed loop operation and will set code after 2 minutes. Both systems can go into open loop after 15 seconds. 14 Coolant temperature sensor signal indicates a temperature of over 275° F for 3 seconds. 15 Coolant temperature sensor signal indicates a temperature colder than -22° F after the engine has been running for 2 minutes. 21 TPS voltage was above 2.5 volts for 2 seconds when the MAP sensor signal showed manifold vacuum to be 15 pounds or more under 1800 RPM. 22 TPS voltage was under 0.2 volts for 2 seconds when the engine was running. 23 Inlet ATS signal showed an air temperature of -22° F after the engine has been running for 1 minute. 24 TPS signal was less than 2% with engine speed between 1400 and 4400 RPM and the MAP signal showed low voltage and high manifold vacuum. Transmission was not in park or neutral. 25 Inlet ATS signal showed an air temperature over 275° F for more than 2 seconds after the engine has been running for 5 minutes and vehicle speed was greater than 44 MPH. 32 EGR open command did not change the fuel mixture when the command was given during off idle operation. EGR opening should cause the mixture to be slightly richer because of the low oxygen content of exhaust gas. 33 MAP sensor signal voltage was too high (low vacuum) for at least 5 seconds when throttle opening was under 2%. 34 MAP sensor signal voltage was too low (high vacuum) when engine speed was under 1200 RPM or when engine speed was over 1200 RPM with throttle opening was over 20%. 35 Idle speed was over 150 RPM outside the desired engine speed commanded by the ECM. 42 The EST signal did not change when the ECM applied bypass voltage to the ignition module. 44 Oxygen sensor voltage was under 0.2 volts for 60 seconds of closed loop operation. 45 Oxygen sensor voltage was above specification. Century and Cutlass Ciera was over 0.75 volts for 50 seconds in a closed loop. Lumina was over 0.7 volts for 30 seconds and throttle angle was between 3% and 45%. 51 PROM error. 53 Charging system voltage was greater than 16.9 volts for more than 50 seconds. Repair charging system.
12 ECM did not receive distributor reference pulses when cam pulses were being received. 13 Oxygen sensor voltage stays between 0.35 and 0.55 volts for 60 seconds during closed loop operation after the engine had been running for 4 minutes and the throttle angle was above 4%. 14 Coolant temperature sensor was shorted showing a high temperature after engine had been running for 2 minutes. 15 Coolant temperature sensor was open showing a low temperature after engine had been running for 5 minutes. 21 TPS was open showing low voltage. 22 TPS voltage was under 0.2 volts for 3 seconds when the engine was running. 23 Mixture control solenoid circuit was either open or shorted. 24 Vehicle speed sensor was out of range after vehicle had been at road speed for 2 minutes. 32 Barometric pressure sensor circuit was low. 34 MAP sensor or vacuum sensor was open or shorted. 35 Idle speed control switch circuit was shorted showing a high TPS reading for over 5 seconds. 41 ECM did not see any distributor reference pulses. 42 The EST signal did not change when the ECM applied bypass voltage to the ignition module. 43 The ESC knock signal lasted too long causing the EST signal to be retarded. 44 Oxygen sensor was lean during closed loop operation after engine had been running for 2 minutes. 45 Oxygen sensor was rich during closed loop operation after engine had been running for 2 minutes. 51 PROM error. 53 EGR valve vacuum was incorrect. 54 Mixture control solenoid circuit was shorted and/or ECM is faulty.
13 Oxygen sensor voltage stays between 0.35 and 0.55 volts for 60 seconds during closed loop operation after the engine had been running for 2 minutes and the throttle angle was above 4%. 14 Coolant temperature sensor signal indicates a temperature of over 275° F for 3 seconds. 15 Coolant temperature sensor signal indicates a temperature colder than -47° F for 3 seconds. 21 TPS voltage was above 2.5 volts for 5 seconds when the MAP sensor signal showed manifold vacuum above 15 pounds or TPS signal voltage was over 4.5 volts. 22 TPS voltage was under 0.2 volts for 3 seconds when the engine was running. 23 Manifold air temperature sensor signal showed an air temperature of -31° F for 3 seconds after the engine has been running for 8 minutes. 24 Vehicle Speed Sensor Sensor/Circuit.When engine speed was between 1400 and 3600 RPM and throttle angle was less than 2%, the MAP sensor signal showed low voltage (High manifold vacuum) for at least 3 seconds. 25 Manifold air temperature sensor signal showed an air temperature over 293° F for more than 3 seconds after the engine has been running for 4 minutes and a vehicle speed was present. 32 EGR vacuum switch was closed during start-up or idle, or EGR vacuum switch did not close when EGR solenoid was commanded to close by ECM for 5 seconds. 33 MAF sensor indicated air flow was more than 20 gm/sec for 2 seconds. 34 MAF sensor signal showed air flow to be less than 2 gm/sec, or the MAF circuit was shorted. 41 The number of crank reference pulses did not match the number according to the PROM when engine speed was under 2000 RPM, or the incorrect PROM has been installed. 42 The EST signal did not change when the ECM applied bypass voltage to the ignition module. 44 Oxygen sensor voltage was under 0.2 volts for 60 seconds of closed loop operation. 45 Oxygen sensor voltage was over 0.7 volts for 30 seconds in a closed loop when throttle angle was between 3% and 45% and engine had been running for at least 1 minute. 51 PROM error. 52 CALPAK error. 53 Charging system voltage was greater than 17.1 volts for 2 seconds. Repair charging system. 54 Fuel pump signal voltage was less than 2 volts for 1.5 seconds. 55 ECM error. Replace ECM.
13 Oxygen sensor voltage stays between 0.35 and 0.55 volts for 60 seconds when the TPS signal was above 4%. The engine had been running for at least 2 minutes. 14 Coolant temperature sensor signal indicates a temperature of over 275° F for 3 seconds. 15 Coolant temperature sensor signal indicates a temperature colder than -38° F for at least 20 seconds. 21 TPS voltage was above 4.3 volts for 10 seconds when engine was running and air flow was less than 17 gm/sec. 22 TPS voltage was under 0.25 volts for 4 seconds when the ignition was on. 23 Manifold air temperature sensor signal showed an air temperature of -31° F for 10 seconds after engine had been running for 4 minutes. 24 Engine speed was between 2200 and 4400 RPM and transmission was not in park or neutral and TPS was less than 2% for 3 seconds. 25 Manifold air temperature sensor signal showed an air temperature over 293° F for 3 seconds when vehicle speed was greater than 3 MPH and engine had been running for 8 minutes. 26 Quad-driver sense voltage showed a low voltage when battery voltage should be present, or the sense voltage showed battery voltage when a low voltage should be present. 32 The ECM opens each EGR control valve during deceleration and monitors the change in manifold vacuum. The code sets when the change in manifold vacuum is outside the normal range. 33 MAP sensor voltage was too high for 4.8 seconds when throttle angle was less than 2%. 34 MAP sensor voltage was too low for 1 second when engine speed was under 600 RPM, or MAP sensor voltage was too low for 1 second when engine speed was over 600 RPM and throttle angle was above 20%. 41 Faulty or incorrect MEM-CAL. 43 Knock sensor signal was either above 3.5 volts or below 1.5 volts for at least 0.5 seconds. 44 Oxygen sensor voltage was under 0.2 volts for at least 60 seconds of closed loop operation. 45 Oxygen sensor voltage was over 0.7 volts for 50 seconds in closed loop operation with a throttle angle between 3% and 45%. 51 MEM-CAL error. 52 CALPAK error. 53 ECM sees a battery voltage of more than 17.1 volts for 2 seconds. 54 Fuel pump voltage was less than 4 volts for 0.4 seconds. 62 Vehicle gear commanded by ECM did not match actual gear selected. 66 A/C pressure sensor voltage was either above 4.9 volts or below 0.1 volts for at least 5 seconds.
13 Oxygen sensor voltage stays between 0.35 and 0.55 volts for 60 seconds. Engine was at normal operating temperature and had been running for at least 2 minutes after start with a throttle angle above 5%. 14 Coolant temperature sensor signal indicates a temperature of over 275° F for 2 seconds. 15 Coolant temperature sensor signal indicates a temperature colder than -27° F for 30 seconds after the engine has been running for at least 30 seconds. 21 TPS voltage was above 2.5 volts for 8 seconds when the MAP sensor signal showed manifold vacuum to be 15 pounds or more. 22 TPS voltage was under 0.2 volts for 2 seconds when the engine was running. 23 Inlet air temperature sensor signal showed an air temperature below -22° F after the engine has been running for 5 minutes. 24 When engine speed was between 1200 and 4400 RPM and throttle position angle was less than 2%, the MAP signal showed low voltage (high manifold vacuum) for at least 5 seconds. 25 Inlet air temperature sensor signal showed an air temperature over 302° F after the engine has been running for 5 minutes. 32 EGR open command did not change MAP sensor signal. Normal EGR flow should cause slight decrease in manifold vacuum which would change MAP sensor signal. 33 MAP sensor signal voltage was too high (low vacuum) for 5 seconds when throttle opening was under 4%. 34 MAP sensor signal voltage was too low (high vacuum) when engine speed was under 1200 RPM or the engine speed was over 1200 RPM with a throttle position angle above 21%. 42 The EST signal did not change when the ECM applied bypass voltage to the ignition module. 43 The ECM did not detect a knock signal during near wide open throttle operation with coolant temperature above 194° F or the knock signal was present for 5 seconds or more during normal engine operation. 44 Oxygen sensor voltage was under 0.2 volts for 50 seconds of closed loop operation. 45 Oxygen sensor voltage was over 0.7 volts for 30 seconds of closed loop operation with a throttle angle between 2% and 20%. 51 PROM error. 52 CALPAK error. 54 Fuel pump voltage was not present at fuel pump sense line for 2 seconds after the ECM has sent the fuel pump on command. 55 ECM error. Replace ECM.
13 Oxygen sensor voltage stays between 0.35 and 0.55 volts for 60 seconds. Engine was at normal operating temperature and had been running for at least 2 minutes after start with a throttle angle above 5%. 14 Coolant temperature sensor signal indicates a temperature of over 275° F for 2 seconds. 15 Coolant temperature sensor signal indicates a temperature colder than -27° F for 30 seconds after the engine has been running for at least 30 seconds. 21 TPS voltage was above 2.5 volts for 8 seconds when the MAP sensor signal showed manifold vacuum to be 15 pounds or more. 22 TPS voltage was under 0.2 volts for when the engine was running. 23 Inlet air temperature sensor signal showed an air temperature below -22° F after the engine has been running for 5 minutes. 24 When engine speed was between 1200 and 4400 RPM and throttle position angle was less than 3%, the MAP signal showed low voltage (high manifold vacuum) for at least 5 seconds. 25 Inlet air temperature sensor signal showed an air temperature over 302° F after the engine has been running for 5 minutes. On Brougham models the inlet air temperature sensor signal shows a temperature above 297° F with an engine speed greater than 35 MPH. 32 EGR open command did not change the MAP sensor signal. Normal EGR flow should cause slight decrease in manifold vacuum which would change MAP sensor signal. 33 MAP sensor signal voltage was too high (low vacuum) for 5 seconds when throttle opening was under 4%. 34 MAP sensor signal voltage was too low (high vacuum) when engine speed was over 1200 RPM. 42 The EST signal did not change when the ECM applied bypass voltage to the ignition module. 43 The ECM did not detect a knock signal during near wide open throttle operation with coolant temperature above 194° F or the knock signal was present for 4 seconds or more during normal engine operation. 44 Oxygen sensor voltage was under 0.25 volts for 50 seconds of closed loop operation. On Brougham models the oxygen sensor voltage was under 0.2 volts. 45 Oxygen sensor voltage was over 0.75 volts for 30 seconds with a throttle angle above 20%. On Brougham models the oxygen sensor voltage was over 0.7 volts. 51 PROM error. 54 Fuel pump voltage was not present at fuel pump sense line for 2 seconds after the ECM has sent the fuel pump on command. 55 ECM error. Replace ECM.
13 Oxygen sensor voltage stays between 0.35 and 0.55 volts for 60 seconds. Engine was at normal operating temperature and had been running for at least 2 minutes after start with a throttle angle above 5%. 14 Coolant temperature sensor signal indicates a temperature of over 266° F for 3 seconds. 15 Coolant temperature sensor signal indicates a temperature colder than -38° F for 3 seconds. 16 High battery voltage OR Direct inition system open or shorted to ground 17 RPM signal problem 21 TPS voltage was above 2.5 volts for 3 seconds when the MAP sensor signal showed manifold vacuum to be 15 pounds or more, or TPS was above 4.8 volts at anytime. 22 TPS voltage was under 0.2 volts for 2 seconds when the engine was running. 23 Manifold air temperature sensor signal showed an air temperature below 22° F after the engine has been running for 5 minutes. 24 When engine speed was between 1400 and 3600 RPM and throttle position angle was less than 2% for at least 4 seconds. 25 Manifold air temperature sensor signal showed an air temperature over 302° F for 2 seconds after the engine has been running for 2 minutes and vehicle speed was greater than 5 MPH. 26 Fault in quad driver module 27 Fault in 2nd gear switch 28 Fault in 3rd gear switch 29 Fault in 4th gear switch 30 N/A 31 Low voltage at manifold absolute pressure sensor OR Fuel injector OR Park or neutral switch OR CAM diagnostic OR Governor malfunction OR Wastegate overboost OR Wastegate eletrical signal open or shorted to ground 32 EGR open command did not change the fuel mixture when the command was given during off idle operation. EGR opening should cause the mixture to be slightly richer because of the low oxygen content of exhaust gas. 33 MAP sensor signal voltage was too high (low vacuum) 34 MAP sensor signal voltage was too low (high vacuum) 35 Idle speed can not be set to desired RPM 36 Burn off at mass air flow sensor OR Problem in transmission shift OR Fault in direct ignition system OR Missing pulses in electronic spark timing signal 37 N/A 38 Fault in torque converter clutch brake switch 39 Fault in torque converter clutch circuit 40 N/A 41 Fault at cam sensor OR Cylinder select error OR Tach input error 42 Fault at electronic spark timing circuit OR Fault at direct ignition system OR Fault at fuel cutoff relay circuit 43 Low voltage at electronic spark timing circuit 44 Oxygen sensor lean 45 Oxygen sensor rich 46 Fault at vehicle anti-theft sytem OR Fault at power steering switch 47 Problem at Electronic Control Module (ECM) 48 Misfire 49 Vacuum leak 50 N/A 51 PROM error 52 Problem at Electronic Control Module (ECM) – Missing fuel calpac missing OR Analog to digital converter error OR Fault at quad driver module OR Low voltage at oil temperature sensor 53 High voltage at battery OR High voltage at exhaust gas recirculation valve OR Voltage reference error OR Problem at vehicle anti-theft system 54 Low voltage at fuel pump OR Low voltage at Fuel pump relay OR Output failure at quad driver module 55 Problem at Electronic Control Module (ECM) – ECM failure OR Serial bus error OR Fuel lean malfunction 56 Low coolant or corrosivity OR Fault in port throttle system vacuum sensor 57 N/A 58 Problem at vehicle anti-theft system 61 Oxygen sensor degraded OR Port throttle system error OR Cruise control problems 62 Gear switch input diagnostics OR High voltage at oil temperature sensor OR Fault in cruise control- vacuum solenoid circuit 63 High voltage at manifold absolute pressure sensor OR Fault in exhaust gas recirculation valve OR Fault at right oxygen sensor 64 Low voltage at manifold absolute pressure sensor OR Fault in exhaust gas recirculation valve OR Right oxygen sensor lean 65 Failure at exhaust gas recirculation valve OR Faulure at injector peak/hold diagnostic OR Right oxygen sensor rich OR Fault at cruise control position sensor 66 Internal reset of Electronic Control Module (ECM) 67 Fault at cruise control switch 68 Fault at cruise control switch 69 Fault at air conditioner pressure switch 88 Internal reset of Electronic Control Module (ECM)