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Chad Farhat
Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 Heating / Air conditioning systems
Category: Chevy
Satisfied Customers: 1562
Experience:  Owner at Carolina Auto Service & Sales , 20 years Experience in Foreign & Domestic vehicles A6 - Electrical / Electronic systems A7 Heating / Air Conditioning systems
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2013 Chevy Suburban LTZ; mileage: 122,200; VIN:

Customer Question

2013 Chevy Suburban LTZ; mileage: 122,200; VIN: 1GNSKKE79DR174615; I was driving normal city driving for about 20 minutes and stopped at a light. Then, all at once, the engine got shaky, the stabilitrak and traction ctrl lights illuminated, & the warning bells dinged. The light turned green, and as I stepped on the gas pedal, the engine felt weak and sputtery. I pulled over at an auto parts store and borrowed their OBDII reader - it gave me a code of P0304 (cylinder 4 misfire). I was able to drive home and noticed that the traction and stabilitrak lights go out at a higher speed and both systems turn back on, then the problem comes back when I'm at idle. But the engine remains sluggish, the shifting is much harder up and down and braking feels unsteady. I can hear light clunking/thunking noises (maybe from the manifold or muffler) when my RPMs are around 1000 to 1500. I got home and changed cyl 4 spark plug, spark plug wire, and coil pack. Reset the computer by OBDII reader and removing the pos batt cable with ignition "on", and got the same issues on the test drive. Also, cylinder 4 IS getting good spark, but the engine performance has no change when I disconnect or reconnect the wire plug from the coil pack. I disconnected/reconnected all the other plugs and the engine idle got rougher and then smoother as required for each one. Any help would be appreciated. Gonna try opening the throttle body next to clean it out.
Submitted: 5 months ago.
Category: Chevy
Expert:  Chad Farhat replied 5 months ago.

Hi my name is ***** ***** i will be assisting you

Expert:  Chad Farhat replied 5 months ago.

The P0304 is the only code in the engine module

when you replaced the #4 did it come back on number #4

does your scanner pull up live data like o2 sensors and fuel trims

do you have fuel pressure tester ,what is your fuel pressure ?

how long you had the truck ,is the coil you replacded looked oem to you or been replaced before

let me know please

Thank You ***** ( aka -Customer)

ASE Certified Tech

Customer: replied 5 months ago.
Also, when I pulled the spark plug, there were no signs of abnormal wear or failure. The spark plug was clean
Expert:  Chad Farhat replied 5 months ago.

ok thats is good , how about the codes ,was it only p0304 coming back , no p0300 ?

Expert:  Chad Farhat replied 5 months ago.

hey i need to step off my desk for 15 minutes i'll be right back with you

thanks

Expert:  Chad Farhat replied 5 months ago.

hey armando i m back

Customer: replied 5 months ago.
I swapped #4 and #1 to see if the issue would change, but the problem stayed at #4. The elec connector plug the coil looked clean and dry too, no corrosion. I would have to borrow the reader again to check the other sensor readings. I'm pretty sure P0304 was the only code. I'll ck again tomorrow. The suburban was purchased used at 100,000 miles and I've had it for 14 months now. This is the first major issue I've had so far. I've changed the oil twice and the trans fluid once. I'll look into getting a fuel press tester tomorrow. The coil packs look all own.
Expert:  Chad Farhat replied 5 months ago.

ok cool armando

I m online from 10 am till 12 pm , I will hep you solve it

if the problem stayed at #4 and u changed spark plug & coil , u either have no power or ground to #4 coil or THE FUEL INJECTOR NO SHOOTING GAS

we talk tomorrow

Thank You ***** ( aka -Customer)

ASE Certified Tech

Expert:  Chad Farhat replied 5 months ago.

also get a test light and check for power at coil & injector connector

and also test for ground at the connector ( u can do that by clipping test light to positive battery terminal and anyting u touch if test light lights up you have found ground

so check that also and let me know tomorrow

Customer: replied 5 months ago.
I tested for grind at the coil pack and all four terminals lit up. When I tested ground at the injector, only one of the two lit up. That was with engine off
Expert:  Chad Farhat replied 5 months ago.
Ok we talking about injector #4 correct? That u checked and you missing ground
Customer: replied 5 months ago.
Right I checked at #4, only one grounded out. With engine off
Customer: replied 5 months ago.
Injector rail is pressurized. Tester says 81 psi
Customer: replied 5 months ago.
Also, I noticed on my drive, the motor computer doesn't switch to V4 or V6 while I'm driving, like it used to before. It just stays in V8 mode
Customer: replied 5 months ago.
I ckd for ground at the injector in front of #4 and that one only had ground on one as well.
Expert:  Chad Farhat replied 5 months ago.
Kind a little high on fuel pressure 50 to 75 u are at 81
Yeah , again no codes right
Expert:  Chad Farhat replied 5 months ago.
How this happened just suddenly , or any prior work contributed to this , can u tell me some history, I m surprised u have no codes , what kind of scanner are you using ,
Let me know
Thanks
Customer: replied 5 months ago.
Service traction control and service stabilitrak messages come up. But I think that is due to the engine degradation
Customer: replied 5 months ago.
Those service messages are only from the vehicle cluster
Customer: replied 5 months ago.
Code reader
Expert:  Chad Farhat replied 5 months ago.
Ok question I ur pic u send me there is an arrow down on the screen indicating another fault press down arrow what is that code
Customer: replied 5 months ago.
Here is a complete scroll thru of the readout
Customer: replied 5 months ago.
Here is a scroll through of a diagnostic check option
Expert:  Chad Farhat replied 5 months ago.
Ok that is great ,give some time to go thru this and get back to you .
It can be , something big, but I don't like u not getting ground to injector, ur not shooting fuel on that injector and u changed the plug and coil and unsawped and it stayed ,this injector can not be firing
Do U have an injector test kit ?
Customer: replied 5 months ago.
havent found an injection test kit
Customer: replied 5 months ago.
We just moved from tx to ga. Maybe the drive placed a strain on the vehicle. I'm hoping it's a sensor or something simple
Expert:  Chad Farhat replied 5 months ago.
I don't believe it is a big problem
Those suburban are pretty tough
And 122k is not a lot ,I m not sure we will seen ,if no fuel injector tester,use a test light,hook up the negative lead of test light to positive battery terminal and now when touch anything and test light lites up ,then you have found ground
How about we try finding ground that way while car running
And come back and insert the test light probe in the back of the fuel injector connector ,one of those 2 wires into the connectors should make the test light pulse On &Off if the injectors is being grounded to shoot fuel if u don't see that the injector is not working that is why the # ***** cylinder keeps throwing this code.or at least let's check to see if that what we have in case you can't fine a fuel injectors tester .Chad (akaCustomer
Customer: replied 5 months ago.
You think maybe throttle position sensor?
Customer: replied 5 months ago.
After resetting the computer, by removing the positive lead on the battery, the problem goes completely away for about 20 - 30 mins. Then returns with the exact same issue (rough idle, weak acceleration, dings, stabilitrak/traction ctrl, rough up & down shift)
Customer: replied 5 months ago.
Just got your last msg... I tested for ground with eng running the light on tester was blinking. When I rem'd the plug, the idle got rougher & when I put it back, it got more stable.
Customer: replied 5 months ago.
I tried removing the coil pack elec connector and there seemed to be no change in eng operation, reconnected that and tried the split plug wire remove and reco, no change in eng op there either but got spark going through for sure
Customer: replied 5 months ago.
spark plug wire
Expert:  Chad Farhat replied 5 months ago.

when u removed it and then plugged and it got better when u plugged means the injector IS working

be honest you i need you to scan this car and get me codes ?

can you do that ?

there must be a fault code in the pending or history file .

at this point ,it could be number of things , but i agree that a module is resetting since it will do good for 20 30 min like u said .

chad(aka-jhook1398)

Expert:  Chad Farhat replied 5 months ago.

the igntion coils go out at this mileage but u said u swaped them and still code #4

so , make sure we good on coils , If no code are provide to me , i really cant help anymore on it cause i will be guessing and i dont like doing that .

so let me know , advance auto or auto zone do the scan for free and give u a print out

Thanks

Chad(aka-jhook1398)

Customer: replied 5 months ago.
Ok I'll get a print out soon
Expert:  Chad Farhat replied 5 months ago.
Ok awesome thank you
Chad
Customer: replied 5 months ago.
Advanced, autozone, and o'reilly's lays don't have a printout feature here. But the Bosch code reader at o'reilly's gave me some different codes. : C0561; P0300; P0202; P0204; and P0354
Expert:  Chad Farhat replied 5 months ago.

DTC P0202 - Injector 2 Control Circuit

DTC P0204 - Injector 4 Control Circuit

This could have been caused by u testing the injector that is why they set by unpluging ,should have cleared codes drive it and scan again but i believe that what happens especially if unhooked injector #2 , because we were working on #4 so i expected to see P0204 but did unplug injector #2 ,let me know that is important

like i suspected there is P0300 multiple engine misfire

DTC P0354 - Ignition Coil 4 Control Circuit but remember you disconnected that plug with key on or running so it will set

DTC C0561 76 - System Disabled Information Stored Below Allowable Range Circuit/System Description The PSCM monitors vehicle speed validity message from the engine control module (ECM) via the serial data circuit. The power steering control module (PSCM) uses this vehicle speed message, along with the torque sensor and motor rotational sensor inputs, to determine the desired amount of steering assist. The PSCM monitors the intermediate voltage power limit request message from the accessory power module (APM) to detect a possible overheating event. The hybrid control module (HCM) sends this message to the PSCM via the serial data gateway module to reduce the APM power output to the PSCM until the APM returns to normal operating temperature. Conditions for Running the DTC Ignition ON. Conditions for Setting the DTC DTC C0561 71 The PSCM receives an invalid, vehicle speed message from the ECM. DTC C0561 76 The PSCM receives the intermediate voltage power limit request message to ramp down the power assist due to a possible APM overheating event. Actions Taken When DTC Sets * DTC is stored in memory. * The driver information center (DIC) displays the SERVICE POWER STEERING warning message. Conditions for Clearing the DTC * A current DTC will clear on the next malfunction free ignition cycle. * A history DTC will clear after 100 consecutive malfunction-free ignition cycles. * Steering assist is reduced. Reference Information Schematic Reference Power Steering Schematics See: Steering > Electrical > Power Steering Schematics Connector End View Reference Component Connector End Views See: Vehicle > Connector Views > Connector End Views By Name Description and Operation Power Steering System Description and Operation (EPS) See: Steering > Components > Power Steering System (EPS)Power Steering System Description and Operation (Hydraulic Power Steering) See: Steering > Components > Power Steering System (Hydraulic Power Steering) Electrical Information Reference * Circuit Testing See: Vehicle > Component Tests and General Diagnostics > Circuit Testing * Connector Repairs See: Vehicle > Component Tests and General Diagnostics > Connector Repairs * Testing for Intermittent Conditions and Poor Connections See: Vehicle > Component Tests and General Diagnostics > Testing for Intermittent Conditions and Poor Connections * Wiring Repairs See: Vehicle > Component Tests and General Diagnostics > Wiring Repairs Scan Tool Reference Control Module References See: Vehicle > Programming and Relearning > Control Module References for scan tool information Circuit/System Verification Verify that no DTCs are set in the ECM or APM. If DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle See: A L L Diagnostic Trouble Codes ( DTC ) > Diagnostic Trouble Code Descriptions > Diagnostic Trouble Code (DTC) List - Vehicle.

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did he clear your codes after the scan or no ?

P0300 is an issue of all your igntion coils are misfiring intermittently , this needs to be checked ,

the C0561 is when the power steering assist module picks up an erratic vehicle speed signal , like a bad wheel speed sensor , does your power steering feels heavy when the car acts up

we have to take care of the P0300

because it could be causing the C0561 do you have (service power steering message on the display

let me know

Thanks

Chad

Customer: replied 5 months ago.
I disconnected and reconnected #2 for comparison. And I did not get a steering msg, but I believe its triggered by whatever else is going on. Steering feels fine. Service stabilitrak and service traction control keep coming back. But I believe those systems are triggered by the eng malfunction as well
Expert:  Chad Farhat replied 5 months ago.

hey i m about to leave my shop and go home ,i like to research this for you this evening and get back to you ,

I will be online till 12 pm

answer this for me , how long u had the vehicle and has the coils been changed previously that u know of and or the spark plug or igntion coil were replaced only #4

Expert:  Chad Farhat replied 5 months ago.

did he clear the codes for you ?

Expert:  Chad Farhat replied 5 months ago.

the reason i m asking is i believe only P0300 will come back again only and if that is true that will give us our answer?

Expert:  Chad Farhat replied 5 months ago.

and also coils all new or only #4 that u replaced now

Expert:  Chad Farhat replied 5 months ago.

do u have an ohmmeter , that we can pull all the igntion coils and test the resistance when they are cold and compare , they should all be the same or very little difference ?

Customer: replied 5 months ago.
I've had the suburban for a little more than a year now. I haven't changed any of the plugs or packs. I bought it used from a Chevy dealership. He did not clear any codes. All the coil packs look like originals. I only swapped two for comparison. I just bought a multimeter but have never used one. I don't know where to place the dial
Customer: replied 5 months ago.
Multimeter
Expert:  Chad Farhat replied 5 months ago.

i can call you if u like to guide thru it ,, it will be like $15 extra

I dont know which meter u have , but you set it on ohms ,I guess put it on auto if u have that feature and u have to leads , put one on each pin , u should read something :)

Chad

Customer: replied 5 months ago.
Ok. Which terminals do touch on the coil pack?
Expert:  Chad Farhat replied 5 months ago.

Put one lead on d and go across the others and see which one will read

Expert:  Chad Farhat replied 5 months ago.

you are not going to hurt anything u just reading ohms (resistance)

Customer: replied 5 months ago.
I'll have a go at it tomorrow morning. At work tonight
Expert:  Chad Farhat replied 5 months ago.

no problem , I will be around tomorrow

chad(aka-jhook1398)

Customer: replied 5 months ago.
Ok I ran across all of the connectors that go into the top of the coil packs. They all read about the same
Expert:  Chad Farhat replied 5 months ago.

hey

ok got it, i like the paper you drew :) very helpfull

they look good , ok this is weird , no problem , let me see what i come up with

Chad

Expert:  Chad Farhat replied 5 months ago.

are you an engineer ? or you do something technical ?

Customer: replied 5 months ago.
I'm an aircraft mechanic in the Air Force. 16 yrs working on airplanes hydraulic/mechanical and used to help my car mechanic dad when I was in my teens.
Customer: replied 5 months ago.
But this car problem is testing my patience, I'm thinking about dropping it off at a mechanic for repair
Expert:  Chad Farhat replied 5 months ago.

i figured that :) good deal

we are missing something here ,i m going to spend sometime today on it

and hopefully you & i can figure it out, have a friend at gm dealer up the road for my shop , i m going to ask him if he came across this and if there any tsb on this or recall or new update info, my system dont show it and mine should be update to the present date

thank you for your patience on this matter wish i had a quick fix, this one is little different since pinpointing the problem is essential at this time cause we will be throwing parts at it.

but i do believe the coils and the plugs needs changing regardless of it will fix the issue or not at this mileage .

I will let you know Sir

Chad (akajhook1398)

Expert:  Chad Farhat replied 5 months ago.

before you take it to shop , changing the coil & plugs you can do yourself and save the labor , if i cant figure out some for you, then obvious it going to take more trouble shoot and local tech with a good scanner should be able to know by looking at the pid values on the screen doing a road test

Customer: replied 5 months ago.
I noticed that they are AC DELCOs
Expert:  Chad Farhat replied 5 months ago.

a/c delco is gm oem brand, so definitely original unless previous owner installed dealer ones, i doubt it , they usualy last up to 100k

Customer: replied 5 months ago.
I'll try changing them. you say coil packs and plugs?
Customer: replied 5 months ago.
Even though they still energize?
Expert:  Chad Farhat replied 5 months ago.

yes you need a scope to read that signal on the coil, that is piercing into the wires straight thru individual leads and read each signal coming to the coil simultaneously and monitor if it is dropping when hot ., and we dont have that equipment now so

i say regular maintenance calls for that at that mileage intervals at least for the spark plugs, a weak spark plug is usualy the cause of a ignition coil failure since it is working over time to fire that plug and you have over 100k now from the date of purchase at a mileage of 100k .

Customer: replied 5 months ago.
Chad, thank very much for your guidance and support in troubleshooting my car problem. I learned a few things as well. Gonna take it in to a shop that can throw multiple test empty on it.
Expert:  Chad Farhat replied 5 months ago.

Thank You you sir

it was great meeting you please do let me know what happens

this post will stay open even after you rate me ,so if you reply back here I will see it

Good Luck

Chad Farhat

ASE Cetified Technician

Hope I was helpfull to you ,Let me know if you need anything else on it

A Positive rating is Much Aprecciated

This Post Will Stay Open for you to Come Back And Ask Me Any Follow Up Questions You May have On This Issue Even after You Rate Me

Thank You

Chad Farhat ( aka -Customer)
ASE Certified Technician