Code 0200 DTC, fuel pump relay fault

DHOOPER

MEMBER
2004 CHEVROLET SUBURBAN
5.3L
V8
4WD
AUTOMATIC
195,000 MILES

1) Challenged by 0300 misfire codes. Replaced, plugs, wires, injectors. 150-155 PSI in each cylinder.

2) 0300 remains and 0200 triggered.

3) Fuel pump continues to operate even though fuel pump relay was removed.

Thoughts?

5 Replies

HMAC300

MECHANIC
48,601 POSTS

Yep, best thing on a misfire is to have a mechanic do it so he can scan the system and check things out as it can be basic problem, sensor, injector, multiple things. It is so you do not waste money on good parts. Auto parts are good for that, they do not know much so they sell you stuff they think it may be. The 200 code is an injector circuit problem which can be anything from a bad injector to a PCM or wiring issue like the harness.

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Friday, March 10th, 2017 AT 9:31 AM

DHOOPER

MEMBER
3 POSTS

Thanks for your prompt reply. Previously, I verified that the number five plug and wire failed and all were replaced since wires were original and plugs had 95,000 miles on them. Resistance test on original injectors showed great disparity ranging from 15.6 - 12.2. Decided to replace them since flow was impaired on three and bench cleaning was not effective. Parts replacement was logic and sound. I just stumbled across your site. Do you folks provide wiring diagrams of the harness? Also, why would the fuel pump continue to operate after the relay is pulled? Does Chevrolet provide an alternate power source to the pump? If so, what could it be? Thanks again for your thoughts?

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Friday, March 10th, 2017 AT 10:00 AM

HMAC300

MECHANIC
48,601 POSTS

The fuel pump is also hooked to the oil pressure switch and relay is mostly for times on start up. The problem with replacing harness is it may not be bad I will send it but you should really have a mechanic see what is causing the misfire. Is this VIN number T or Z because they can be different?

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Friday, March 10th, 2017 AT 12:03 PM

DHOOPER

MEMBER
3 POSTS

This is a Flex Fuel Z vehicle. I share your concerns about sound diagnostics performed by a pro, but have not reached that point yet. Unfortunately getting close. Nothing was attached if you sent me a diagram. Thanks again!

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Friday, March 10th, 2017 AT 12:15 PM

HMAC300

MECHANIC
48,601 POSTS

I did not send a diagram because of the VIN had to find out which it was first. The wires may have a connection right at back of engine under manifold so check there as the wires show going right back to PCM. You might check wire going to PCM on offending cylinder and see if it has a good connection normally under five ohms per wire. Also make sure to check injector one and two fuses in fuse box under hood. Numbers on PCM correspond with wires and are numbered on plastic connections at PCM.

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