Check Engine light comes on after a few minutes

I got it scanned, I was a dummy and didnt write down the code but I think it was 538 but after searching, it doesnt seem right...

Mechanic said could be o2 sensor, fuel pump, or vacuum leak.

I just got the oil change done and dropped in a K&N air filter, could that cause a problem? It's got 168k+ miles

Thoughts? thanks!

yo Not,

you can do the Test in your driveway w/just a paper clip or short length of wire;

Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19

http://broncozone.com/topic/14269-code-reader/?pid=74587&mode=threaded

A helper is good to assist in reading Codes; best is to take a cell fone vid and replay it.

Some basics;

Visual Check

1.Inspect the air cleaner and inlet ducting.

2.Check all engine vacuum hoses for damage, leaks, cracks, blockage, proper routing, etc.

3.Check EEC system wiring harness for proper connections, bent or broken pins, corrosion, loose wires, proper routing, etc.

4.Check the Powertrain Control Module (PCM), sensors and actuators for physical damage; IAC, TPS I see was replaced, etc.5.Check the engine coolant for proper level and mixture.

6.Check the transmission fluid level and quality. See E4OD Fluid Condition Check Below)

7.Make all necessary repairs before continuing

8. Check headlights

The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test.

Run it around to heat the engine up and shift thru all gears including Reverse.

Make sure A/C is off and transmission is in Park (automatic); or in Neutral for a Manual & release clutch.

Turn off all accessories; radio, lights, A/C, heater, blower, fans, etc. (close driver's door)

Then turn off engine and wait 10 seconds.

Do KOEO test First

Post Code(s) here according to:

KOEO

&

KOER

The Self-Test is divided into three specialized tests: Key On Engine Off Self-Test, Engine Running Self-Test, and Continuous Self-Test. The Self-Test is not a conclusive test by itself, but is used as a part of the functional Quick-Test diagnostic procedure. The PCM stores the Self-Test program in permanent memory. When activated, Self-Test checks the EEC system by testing memory integrity and processing capability, and verifies that various sensors and actuators are connected and operating properly.

The Key On Engine Off and Engine Running Self-Tests are functional tests which only detect faults present at the time of the Self-Test. Continuous Self-Test is performed during normal vehicle operation and stores any fault information in Keep Alive Memory (KAM) for retrieval at a later time.

Key On Engine Off Self-Test

At this time, a test of the EEC system is conducted with power applied and engine at rest.

To detect errors during Key On Engine Off Self-Test, the fault must be present at the time of testing.

Continuous Memory DTCs are issued as a result of information stored during Continuous Self-Test, while the vehicle was in normal operation. These DTCs are displayed only during Key On Engine Off Self-Test and after the separator pulse. Intermittent faults that have not occurred in the last 80 warm-up cycles (40 cycles on some applications) are erased from Continuous Memory and will not produce a Continuous Memory DTC.Note: The separator pulse and Continuous Memory DTCs follow Key On Engine Off DTCs ONLY.

Engine Running Self-Test

At this time, a test of the EEC system is conducted with the engine running. The sensors are checked under actual operating conditions and at normal operating temperatures. The actuators are exercised and checked for expected results.

538 Insufficient RPM change during KOER dynamic response test/ Operator error

yo,

btw, To get accurate info when posting Qs, soon in your profile, include your year, Model (XLT, etc.) engine size; transmission, transfer case, locking hub types and any major mods such as body or suspension lift.

Left Click your name in upper right corner; in pop-up left Click on My Profile

Below an Ad, in right side. Left Click Edit my Profile

In Left Side, Left Click Change Signature

I'll look for any 2 Sensor related codes

DTC 136-Left front Heated Oxygen Sensor (HO2S) lean Possible Causes: Fuel injectors, HO2S, Secondary Air Injection (AIR) system, Positive Crankcase Ventilation (PCV) /Hose, Vacuum, Evaporative Cannister Purge, Manifold Absolute Pressure (MAP) sensor, Electronic Ignition Coil Failure

DTC 172 lean Heated O2; "...Backprobe the MAF (+) and MAF-RTN (-) lines with a DVOM. You should see ~1.0V or slightly less at warm idle. If not, check the +12V and GND lines to make sure there's battery voltage between those terminals with the ignition key turned ON. You also may want to try using the proper spray cleaner on the MAF wires, especially if you have a K&N oily filter (in which case I can almost guarantee there's oily junk on your MAF's wires). Also make certain that the tube(s) leading from the MAF to the throttle body are 100% intact. The red wire (on the right in the first above picture) is supposed to have battery voltage with the key on. Measure between that wire and the one right next to it. You measure the MAF voltage at idle, because the MAF voltage is what's interpreted by the PCM..."

Source: by SigEpBlue

DTC 172, 173 or 41 for HO2S Failure Or Fuse \"E\" Inoperative, ABS Light On, Back-Up Lamps Inoperative, Daytime Running Lamp (DRL) Inoperative, MIL On, Inadvertent Self-Test, Speedometer Inoperative & Trailer Battery Charge Relay Inoperative in TSB 95-5-21 for 92-95 Bronco & F Series; "...the HO2S wires in the 12A690 (subassembly of the 14B060 battery cable) harness may become chafed and the vehicle could exhibit any one of the following conditions....Lack of proper HEGO operation may cause, or be the result of a rich or lean fuel condition, which could cause additional heat in the catalyst. Perform self test KOEO and KOER, service any codes. CHECK FOR PROPER HEGO GROUND. If the HEGO ground is good, the following areas may be at fault: ..."

DTC 172, 173 or 41, Common Locations for Short Circuits TSB 95-02-11 on 94-95 Bronco & Trucks; "the HO2S wires in the 12A690 (subassembly of the 14B060 battery cable) harness may be cut on the lower right engine mount causing improper signals to be sent to the PCM. Damage may be under the electrical tape.

DTC 542 "...No Start: Inertia Fuel Shutoff (IFS) switch not reset or electrically open. Open circuit between the fuel pump and FPM circuit connection to the power-to-pump circuit. Poor fuel pump ground. Fuel pump electrically open. Engine Starts: Fuel pump secondary circuit short to power. Fuel pump relay contacts always closed. Open in FPM circuit between PCM and connection to the power-to-pump circuit. Left/front HO2S short to power (dual HO2S applications) Damaged Powertrain Control Module (PCM). Does the engine start? (For trucks with dual fuel tanks, verify tank selector is in the same position it was when KOEO DTC 542 was received.) Yes GO to J11. No GO to J15..."

DTC 542 (O,M) Fuel pump open, bad ground or always on; Check inertia fuel shutoff switch; behind passenger side kick panel. No Start: Inertia Fuel Shutoff (IFS) switch not reset or electrically open. Open circuit between the fuel pump and FPM circuit connection to the power-to-pump circuit. Poor fuel pump ground. Fuel pump electrically open. Engine Starts: Fuel pump secondary circuit short to power. Fuel pump relay contacts always closed. Open in FPM circuit between PCM and connection to the power-to-pump circuit. Left/front HO2S short to power (dual HO2S applications). Damaged Powertrain Control Module (PCM).

Source: by miesk5 at Ford Bronco Zone Forums 2

As you can see, an O2 "related" Code may not mean the sensor is bad; so save $$ and find the Code, post it and we'll try to get the pin-point test for you

Thanks miesk!

NotOJ said:

Mechanic said could be o2 sensor, fuel pump, or vacuum leak.

I just got the oil change done and dropped in a K&N air filter, could that cause a problem? It's got 168k+ miles

Click to expand...

Usually the o2 sensor is not the problem, it is just reporting the problem.  When you dropped in the K&N did you by any chance bypass the MAF sensor or did you use a square one that fits into the air box?  If so, that is probably what is turning on the "check engine" light.