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Jason
Jason, Auto Service Technician
Category: Chevy
Satisfied Customers: 264
Experience:  ASE MASTER TECH L1 ADVANCED DIAG, 18 YEARS EXP, 6 YEARS GM TECH, 12 YEARS ALL MAKES ALL MODELS
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i have code p1351 on 1998 chevy blazer

Customer Question

i have code p1351 on 1998 chevy blazer
Submitted: 2 years ago.
Category: Chevy
Expert:  JOHN aka Eauto replied 2 years ago.
Hi . Thank you for asking your question on JustAnswer.ok drop the fuel tank, replace the fuel pump, flush the fuel lines, and refill it with fresh fuel, im 100% sure that will fix your problem, the problem is the fuel pressure is dropping at times and the computer is trying to adjust the secondary ignition out put voltage accordingly, im 100% because i had one with this problem last month with that same code and the customer had done replaced all the same parts you have(which made my job easier). good luck. and please accept my answer.


Thank you again for trusting us with your problem. John aka eauto
Customer: replied 2 years ago.
i have dropped tank, replaced fuel pump, flushed lines. also, i have replace oil pressure sensor, fuel pump relay and fuel tank pressure sensor. have power to new fuel pump at wiring pig tail but pump doesnt run with key on or start up. between all the changes i tested the pump with battery and it does work. i dont know why i have power coming to pump but just not working. i also have checked ground wire.
Expert:  JOHN aka Eauto replied 2 years ago.
what brand pump? there is poer to the pump and it does not turn on?
Customer: replied 2 years ago.
airtex brand from advanced auto. yes, i have 12 volts at plug for about 5 seconds and then power stops. during that 5 second period the fuel pump still doesnt make any noise and vehicle wont start. this problem started when i went to start up in morning. so , with out checking i just decided to change fuel pump and after replacing pump and still wouldnt start. i tested for power and even took old pump and hooked up to battery and it ran. but when i hook it up to wiring it doesnt. there is 12 volts coming through grey wire and gas gauge seems to work. but neither new pump in taqnk or old pump will run when plugged in.
Expert:  JOHN aka Eauto replied 2 years ago.
does it have a good ground.....i have had terrible luck with airtex pumps....i refuse to install them.i have had more failures then i would like to talk about....did you replace the pig tail?
Customer: replied 2 years ago.
yes, i replace the pig tail. solderd wires and put heat shrink and tape. i have also cleaned ground. even the old pump, that was not airtex wont run when plugged in but will run off of straight battery power. i dont think its pump related and it wasnt the fuel pump to start being it runs from battery. i did install the new pig tail and tried old pump plugged in to it and still didnt run. just doesnt make sense with power to and nothing happening to either pump. i dont know if there is a relay or what that i havent changed that is causing this. i have changed everything i know of, relay, fuse and even pump. truck drove good day before, wouldnt start next morning and now i have this just by sitting over night.
Expert:  Jason replied 2 years ago.

with this code you do have a electrical problem from the pcm to the relay, i will look up what you should do next...

Customer: replied 2 years ago.
will you let me know what to check next?
Expert:  Jason replied 2 years ago.

THE FIRST THING TO DO IS FOLLOW THE FLOW CHART FOR THE CODE... IT IS NOT FOR THE RELAY AS I THOUGHT IT IS FOR A PCM INPUT............. HERE IS THE FLOW CHART FOR THE DIAGNOSIS.

 

 

CIRCUIT DESCRIPTION

The enhanced ignition system uses the crank sensor in order to provide the timing input to the Vehicle Control Module (VCM). The VCM uses this reference pulse in order to determine the individual ignition spark timing for each cylinder

Once the VCM calculates the ignition timing, the ignition coil module on the Ignition Control (IC) circuit receives the timing signal. Each timing pulse received by the ignition coil module on the IC circuit triggers the coil module in order to operate the ignition coil. The secondary ignition voltage is induced, and then the secondary ignition voltage is sent to the distributor for distribution to each spark plug.

The IC signal voltage ranges from about 0.5 volt to 4.5 volts.

CONDITIONS FOR SETTING THE DTC

  • The EST is enabled.
  • The engine speed is less than 250 RPM.

ACTION TAKEN WHEN THE DTC SETS

  • The VCM turns the Malfunction Indicator Lamp (MIL) ON when this DTC is reported and one failure has occurred.
  • The VCM records the operating conditions at the time the Diagnostic Fails. Freeze Frame and Failure Records store this information.

CONDITIONS FOR CLEARING THE MIL/DTC

  • The VCM turns the MIL OFF after 3 consecutive drive trips when the test has Run and Passed and not Failed.
  • A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22°C (40°F) from the start-up coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during the same ignition cycle).
  • Use the scan tool Clear Information function.
  • Disconnect the VCM battery feed for 30 seconds.

DIAGNOSTIC AIDS

A poor connection, a rubbed through wire in the insulation, or a wire broken inside the insulation will cause an intermittent.

Check for the following conditions:

  • Poor connection.
  • Damaged harness: Inspect the VCM harness connectors for the following conditions:
  • Backed out terminals CLR 9 and BLK 18.
  • Improper mating.
  • Broken locks.
  • Improperly formed or damaged terminals.
  • A poor terminal to wire connection.

AND

  • Damage to the harness.
  • Intermittent test - If the connections and the harness check OK, monitor a digital voltmeter connected between VCM terminal CLR 9 and BLK 18 while moving related connectors and wiring harness. If the failure is induced, the voltage reading will change. This may help to isolate the location of the malfunction.

TEST DESCRIPTION

The numbers below refer to the step numbers in the diagnostic table.

  1. This determines if the DTC is an intermittent.
  2. This check determines if the IC signal from the VCM is available at the ignition coil driver.
  3. The remaining tests begin to check that the coil driver circuitry is OK.

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Customer: replied 2 years ago.
this would cause the fuel pump to not work when key turned on?
Expert:  Jason replied 2 years ago.
DOES THE FUEL PUMP RELAY CLICK WHEN YOU TURN THE KEY ON?
Expert:  Jason replied 2 years ago.

The main thing you need to do is check for voltage when the pump is plugged in, it must have a load on the circuits you are checking, you can not rely on the voltage readings with no load on the wires, back probe the connector at the pump, use two paper clips pushed in the back of the connector, then check for 12 volts, if no 12 volts then move your ground lead to frame, if you have 12 volts then it is the ground wire, if still no 12 volts, then it is between the relay and the pump, the most common place is the terminals where the relay plug in.

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