Code P1151 - '98 B4000

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Mar 11, 2004 | 07:31 PM

Mazda Owner

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From: Huntington Beach

Code P1151 - '98 B4000

I got the code "P1151" when the check engine light came on. Earlier today I heard a howling type of noise from the engine that I thought was possibly the power steering but now I think it might have been the IAC after reading some threads here. Any ideas?

Mar 11, 2004 | 09:04 PM

hreed

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Look at the technical notes "sticky" at the beginning of this forum. 1151 is an O2 Sensor. The Haynes manual for a PO151 is the upstream oxygen sensor circuit low (bank 2). More info is at obdII.com.

Mar 11, 2004 | 09:08 PM

Rockledge

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P1151 - "Lack of HO2S-21 Switch, Sensor Indicates Lean"

P1151 indicates that the fuel/air ratio is correcting rich for an overly lean condition.

HO2S-21 is the driver's side (Bank 2) Oxygen Sensor mounted before (upstream of) the catalytic convertor. Diagram here.

So you want to figure out why your system is getting too much air and/or too little fuel. The most common culprits are:

-- Failing fuel pump

-- Leaking fuel pressure regulator

-- Low fuel pressure

-- Clogged fuel injector or fuel filter

-- Vapor recovery system.

-- Air leaks after the MAF.

-- Vacuum leaks (vacuum lines and gaskets).

-- PCV system breakdown.

-- Improperly seated engine oil dipstick.

-- Leaking EGR valve gasket.

-- Stuck open EGR valve.

-- Leaking EGR diaphragm.

-- Exhaust leaks before or near the HO2Ss.

Last edited by Rockledge; Mar 11, 2004 at 09:10 PM.

Mar 13, 2004 | 06:52 PM

Mazda Owner

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Is there an easy way to narrow this down? I am not very confident in my diagnostic abilities and even after reading the tech tips I am still confused. Is the EGR valve and the DPIF valve the same thing?

Mar 13, 2004 | 07:04 PM

hreed

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The EGR (exhaust gas recirculation) and the DPFE (differential pressure feedback EGR) are two different things. The EGR is located on the left side of the engine about in the middle. Not sure about the DPFE, but I think it's on the right side. These are vacuum activated, so a quick check would be to put a vacuum guage on the engine and see what you have. The guage is pretty cheap and worth the investment.

Mar 13, 2004 | 09:20 PM

Rockledge

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The EGR Valve looks something like this:

A picture and test of the DPFE Sensor can be found here:

- DPFE Vacuum & Voltage Test

Since you haven't got an EGR-related code, I would probably focus on possible air/vacuum leaks or possible fuel delivery related problems, and rule those out first. Then come back to the EGR system if the lean condition persists.

Mar 14, 2004 | 07:25 PM

Lil red_ranger

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From: Down the road,Tx.

Quote:

Originally posted by Rockledge
The EGR Valve looks something like this:

A picture and test of the DPFE Sensor can be found here:

- DPFE Vacuum & Voltage Test

Since you haven't got an EGR-related code, I would probably focus on possible air/vacuum leaks or possible fuel delivery related problems, and rule those out first. Then come back to the EGR system if the lean condition persists.

Is the egr valve located on the back of the engine ?,also i can't find anything that looks like the DPFE on the front of the engine,any help would be appreciated.My mileage is down to 14.1 and i'm thinking one of these might be the problem
Engine is the 4.0 in a 94 ranger.
Thanks for any help.