Basic LS1 troubleshooting


Basic Troubleshooting

You should hear the fuel pump come on for about two seconds and stop, when you first turn the ignition key to the “on” position. It helps to have a fuel pressure gauge hooked up to the gauge port on the fuel rail.


LS1 fuel port is located on front L/H fuel rail.           The Vortec intake fuel port is on the R/H fuel rail.


Fuel pressure should be at 50-60 PSI when the fuel lines are fully purged of air. When the engine starts and is at idle pressure should be at 53-65 PSI, anything out of this range is concern to be investigated and remedied.


The check engine lamp (known as a Malfunction Indicator Lamp-MIL) should be on with the key to the “on” position. The lamp should go out a few seconds after the engine starts. If it goes off and then comes back on in a short time, the pcm has detected a problem and this will have to be corrected.


If the engine starts and runs rough, and the check engine lamp is on, check the codes with a scanner tool to retrieve the trouble codes, check fuel pressure. Also a bad sensor can cause a rough running condition and if you are using used parts (including the injectors) suspect you may have a bad sensor. This is especially true if the scan tool points to a bad sensor.  

NOTE: A code indicates a particular problem, and may not be a specific part as all the fuel injection system works together. Some bad sensors will not activate the check engine lamp. You will need to follow recommended troubleshooting procedure for your particular YEAR and MODEL of LS1 or Vortec V8 engine.


 The DLC- the pcm’s link to the world.          The OBD II scanner is your friend in the digital world.

MAF sensor problem- If the engine idles, but will not respond with a smooth idle, disconnect the MAF sensor and tap the throttle and see if it responds better. If it does, replace MAF sensor.

TPS- Engine idles rough and is sluggish in throttle response. Shut off engine and turn ignition key to “on” position (engine off). With your scanner tool hooked up, monitor TPS position by opening and closing the throttle, it should respond smoothly from 0 to 100%. If it jumps erratically, replace sensor.

CRANK SENSOR- If this sensor is not responding correctly, it will run erratic, and the injector-coil synchronizing pulse will be incorrect. If the sensor is bad (no crank pulses detected) the engine will not run at all.

Typical Readings for a 1999 LS1 engine, automatic transmission:

·          Engine Speed- 650 rpm

·          ECT- 180 degrees F

·          IAT- 80-100 degrees F

·          MAP- 45 Kpa

·          MAF- 6-10 grams/second

·          IAC position- 10-30 counts, auto trans. In park

·          TPS- 0%

·          Injector Bank 1 PWM- 2.6 ms

·          Injector Bank 2 PWM- 2.6 ms

·          CMP sensor- Low to High (should be counting up)

·          CKP sensor- Low to High (should be counting up)

·          Spark Advance- 15-25 degrees (changing rapidly)

·          Knock retard-0 degrees

·          VSS- 0 mph

·          Ignition Signal 13-14 volts


DTC Trouble codes   OBD II-  Not all codes will apply to all models.  Courtesy of



P0030- heater control circuit bank 1 sensor 1 P0338-CKP sensor- high duty cycle P0742- TCC clutch system stuck on P2135- TPS malfunction 
P0036-HO2S- heater control circuit bank 1 sensor 2 P0339- CKP sensor- intermittent signal loss P0748- Pressure control valve solenoid P2138- APP sensors 1&2 malfunction
P0050- HO2S- heater control circuit bank 2 sensor 1 P0340-Camshaft(CMP)-sensor circuit malfunction P0751- 1-2 shift solenoid performance P2636- Fuel pump malfunction 
P0053-HO2S- sensor resistance out of range  bank 1 sensor 1 P0341- CMP signal mismatch with stored values P0752- 1-2 shift solenoid (4L60E U0107- Comm. fault with throttle actuator control module 
P0054- HO2S- sensor resistance out of range  bank 2 sensor 1 P0342- CMP signal constantly low P0753- 1-2 shift solenoid circuit
P0343- CMP signal constantly high 
P0056- HO2S- sensor heater circuit bank 2 sensor 2 P0344-CMP signal constantly high P0756- 2-3 shift solenoid performance
P0059- HO2S- sensor resistance range bank 1 sensor 2 P0351-Ignition coil (IC) circuit out of range - Coil 1 P0758- 2-3 shift solenoid circuit 
P0060- HO2S- sensor resistance range bank 2 sensor 2 P0352-Ignition coil (IC) circuit out of range - Coil 2 P0785- 2-3 shift solenoid circuit
P0801- Reverse inhibit control solenoid circuit 
P0068- MAF sensor- difference in air flow  P0353-Ignition coil (IC) circuit out of range - Coil 3 P1106- MAP sensor intermittent high voltage
P0101 Mass Air Flow Performance P0354-Ignition coil (IC) circuit out of range - Coil 4 P1107- MAP sensor intermittent low voltage
P0102  MAF Sensor -Low Frequency P0355-Ignition coil (IC) circuit out of range - Coil 5 P1111- IAT sensor-intermittent high voltage
P0103- MAF Sensor- High Frequency P0356-Ignition coil (IC) circuit out of range - Coil 6 P1112- IAT sensor-intermittent low voltage
P0106- MAP sensor signal out of range P0357-Ignition coil (IC) circuit out of range - Coil 7 P1114- ECT sensor intermittent high voltage
P0107-MAP Sensor-Low Voltage P0358-Ignition coil (IC) circuit out of range - Coil 8 P1115- ECT sensor intermittent low voltage
P0400- EGR flow fault
P0108- MAP Sensor- High Voltage P0401- EGR system-insufficient flow P1121- TPS sensor intermittent high voltage
P0402- EGR excessive flow detected
P0403- EGR solenoid control circuit
P0112- IAT Sensor Low Voltage P0404- EGR system-open position performance P1122- TPS sensor intermittent low voltage
P0113- IAT Sensor High Voltage P0405- EGR system-position sensor circuit- low voltage P1125- Accelerator pedal position sensor malfunction
P0116- Temperature difference ECT and IAT- not within calibration range P0410- Secondary Air (AIR) Reaction system fault P1133-HO2S- bank 1 sensor 1-insufficient switching 
P0412- Secondary Air (AIR) solenoid control circuit
P0117- ECT Sensor- Low Voltage P0418- Secondary Air (AIR) pump relay control fault P1134-HO2S- bank 1 sensor 1-insufficient switching 
P0118- ECT Sensor- High Voltage P0420- Catalyst system- bank1 (4.3L V6 ) low efficiency  P1153-HO2S- bank 2 sensor 1-insufficient switching 
P0120- TPS sensor #1 out of range  (TAC) P0420- Catalyst system- bank1 (4.8-5.3-6.0L ) low efficiency P1154-HO2S- bank 2 sensor 1-insufficient switching 
P0421- CMP signal constantly low
P0121- TPS Performance P0430- Catalyst system- bank2 (4.3L V6 ) low efficiency  P1220- TPS out of range
P0122- TPS Circuit- Low Voltage P0430- Catalyst system- bank2 (4.8-5.3-6.0L ) low efficiency P1221- TPS- sensor range discrepancy (TAC)
P0431- Catalyst system - low efficiency Bank 2 
P0123-TPS Circuit- High Voltage P0440- EVAP system malfunction P1258- Engine coolant over temperature
P0441- EVAP-incorrect purge flow 
P0125- ECT  Excessive time to close loop  P0442- EVAP system- small leak detected P1275- Accelerator pedal position (APP) sensor voltage
P0128- ECT  does not meet minimum thermostat setting P0443- EVAP-canister purge valve-incorrect voltage P1276- APP-discrepancy between two sensors
P0131- HO2S Circuit- Low Voltage- Bank 1 Sensor 1 P0446- EVAP-canister purge valve-incorrect voltage P1280- APP- sensors 1&2 discrepancy
P0132- HO2S Circuit- High Voltage- Bank 1 Sensor 1 P0449- EVAP-canister vent valve-incorrect voltage P1281- APP- sensors 1,2 & 3 discrepancy
P0133-HO2S Circuit- Slow Response- Bank 1 Sensor 1 P0451- Fuel tank pressure sensor malfunction  P1285- APP sensor 3 out of range
P0134-HO2S  Insufficient Activity- Bank 1 Sensor 1 P0452- Fuel tank pressure sensor low voltage P1286- APP sensors 3&1, 3&2 discrepancy
P0135- HO2S- Heater Circuit- Bank 1 Sensor 1 P0453- Fuel tank pressure sensor high voltage P1336- CKP  sensor variation not learned
P0136- HO2S- signal out of range bank 1 sensor 2 P0454- Fuel tank pressure sensor-pcm diagnostics P1345- CKP/CMP sensor correlation 
P0137- HO2S- low voltage bank 1 sensor 2 P0455- EVAP- vacuum level low P1351- Ignition control circuit high voltage
P0138- HO2S- high voltage bank 1 sensor 2 P0461- Fuel level sensor performance P1361- Ignition control circuit low voltage
P0140- HO2S- insufficient activity bank 1 sensor 2 P0462- Fuel level sensor circuit  low voltage P1380-ECBM- rough road sensing error
P0141- HO2S- heater circuit malfunction- bank 1 sensor 2
P0143- HO2S Circuit- Low Voltage- Bank 1 Sensor 2 P0463- Fuel level sensor circuit  high voltage P1381-ECBM- No serial data received.
P0480- Cooling fan #1 control circuit
P0481- Cooling fan #2 & 3  control circuit
P0144-HO2S Circuit- Low Voltage- Bank 1 Sensor 2 P0496- EVAP- excessive intake manifold vacuum P1400- Cold start emission reduction system malfunction
P0146-HO2S Insufficient Activity- Bank 1 Sensor 2 P0500-Vehicle Speed Sensor (VSS) Circuit P1404- EGR pintle in closed position 
P0147-HO2S Heater Circuit- Bank 1 Sensor 2 P0502- (VSS) Circuit low output P1415-AIR system malfunction- left bank
P0151- HO2S Circuit- Low Voltage- Bank 2 Sensor 1 P0503- (VSS) intermittent signal  P1416-AIR system malfunction- right bank
P0152- HO2S Circuit- High Voltage- Bank 2 Sensor 1 P0506- Idle speed out of range (lower than expected) P1441- EVAP flow during no purge cycle
P0153- HO2S Circuit- Slow response- Bank 2 Sensor 1 P0507- Idle speed out of range (higher  than expected) P1508-Idle speed too low
P0530- A/C pressure sensor circuit 
P0560- System voltage too low 
P0154- HO2S-Insufficient Activity - Bank 2 Sensor 1 P0562- System voltage too low P1509- Idle speed too high
P0155- HO2S-Heater Circuit - Bank 2 Sensor 1 P0563- System voltage too high P1514-MAF , air flow detected different from predicted
P0567- Cruise control resume switch circuit
P0568- Cruise control resume switch circuit
P0571- Cruise control brake switch circuit
P0156- HO2S-Slow response - Bank 2 Sensor 2 P0601- PCM failure P1515- TPS difference in actual and detected
P0157- HO2S-Low Voltage - Bank 2 Sensor 2 P0602- PCM not programmed P1516- TPS, sensor out of range
P0158- HO2S-High Voltage - Bank 2 Sensor 2 P0603- PCM Long term memory reset P1517-Throttle actuator-failed internal data test  (TAC)
P0160- HO2S- Insufficient Activity- Bank 2 Sensor 2 P0604- PCM Random Access Memory (RAM) P1518-Throttle actuator-invalid or missing data   (TAC)
P0161- HO2S- Heater Circuit- Bank 2 Sensor 2 P0605- PCM Read Only  Memory (ROM) P1600- PCM malfunction
P0169-Ambient fuel temperature high (E85) P0608- VSS output circuit P1621- PCM memory performance
P0171- Fuel Trim System Lean- Bank 1 P0607- PCM malfunction (limited processing) P1626- Serial data comm. fault with VATS controller
P0620- Alternator malfunction 
P0172- Fuel Trim System Rich - Bank 1 P0641-5V Ref. to TPS, Oil Press, MAP or EGR out of range P1627- PCM malfunction -indeterminate fault
P0645- A/C clutch relay control circuit
P0174-Fuel Trim System Lean- Bank 2 P0650- Incorrect voltage to the MIL control circuit P1631- Theft deterrent  (VATS) password incorrect
P0175-Fuel Trim System Rich- Bank 2 P0651- 5V ref. to fuel tank press. sensor out of range P1635- 5V reference circuit 
P0178- Fuel composition sensor freq. out of range (E85) P0654- Tachometer control circuit P1637- Alternator "L" terminal circuit
P0179- Fuel composition sensor contaminated fuel (E85) P0704- Clutch start switch circuit (manual trans.) P1639- 5V reference circuit
P0191- Injector pressure sensor system performance
P0200- Fuel Injector Control Circuit-incorrect voltage P0705- Transmission Range Switch circuit malfunction  P1680- PCM malfunction 
P0201- Injector 1 control circuit
P0202- Injector 2 control circuit
P0203- Injector 3 control circuit
P0204- Injector 4 control circuit
P0205- Injector 5 control circuit
P0206- Injector 6 control circuit
P0218- Transmission Fluid temp. too high P0706- Transmission P/N  Switch circuit performance P1681- PCM malfunction 
P0220- TP Sensor  #2-outside range- TAC only P0711- Trans. Fluid temp (TFT) circuit  out of range P1683- PCM flash memory performance
P0230- Fuel Pump circuit driver command voltage P0712- TFT sensor circuit low voltage  P1810- Transmission press. sw. assembly malfunction 
P0300- Engine misfire detected P0713- TFT sensor circuit high voltage  P1860- TCC pulse width modulator solenoid circuit
P0301- Cylinder 1 misfire detected
P0302- Cylinder 2 misfire detected
P0303- Cylinder 3 misfire detected
P0304- Cylinder 4 misfire detected
P0315-Crankshaft position-(CKP) values not stored in PCM P0716- Input speed sensor circuit out  of range P1870- Transmission slipping 
P0325- Knock sensor circuit malfunction P0717- Input speed sensor circuit no signal P1875- 4WD low switch circuit
P0326- Knock sensor performance
P0327-Knock sensor freq. signal out of range P0719- TCC brake switch circuit low P2101- Control module throttle position actuator position 
P0332-Knock sensor freq. signal out of range P0724- TCC brake switch circuit high P2108- Control module throttle position actuator position 
P0335- CKP sensor- no signal response for 3 seconds P0730- Incorrect gear ratio P2120- APP sensor 1 malfunction  (TAC)
P0336-CKP sensor- signal input incorrect for 3 seconds P0740- TCC enable solenoid circuit P2121- APP sensor 1 malfunction  (TAC)
P0337- CKP sensor- low duty cycle P0741- TCC clutch system stuck off P2125- APP sensor 2 malfunction (TAC)

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