Hi,
Basically my 89 IROC with the L98 (MAF) started throwing code 36 last night. I beleive its happened before but not consistantly. Now its throwing the code everytime I start the car. I changed the two matching relays on the firewall by the break booster, and it stayed code 36. I'm planning on replacing the middle relay 149701(similar numbers, square in shape) since the contacts dont look too good, along with the fact that i was able to pull the harness off that relay start the car and again only get code 36. Im hoping my problems this simple and would appreciate any other ideas what could cause this? Also it seems like the SES light comes on a few seconds after I turn the car on, as soon as the rpms drop down below a thousand (like normal) and the light comes on. If I keep the rpms on the light still comes on around the same time. Thanks in advance!

Martin

 

code 36 Burn off at mass air flow sensor OR
Problem in transmission shift OR
Fault in direct ignition system OR
Missing pulses in electronic spark timing signal

 

Martin,

Some days, 1ZNF.

Anyway, check the electrical connector at the MAF sensor. A poor connection there may cause the ECM to detect a burn-off failure.

Just for the archives, there is a rare condition that can cause a "false" code 36. Look closely at the schematic for the circuit, and you will see that the auxilliary oil pressure switch can cause the MAF power relay to remain energized long after the engine has been shut off. This is normally not a problem, but can get you really confused at times.

You'll need the following diagram to follow the story:



The sequence of MAF operation is supposed to be as follows:

Key On - The MAF power relay is energized, providing B+ to the MAF terminal "E", enabling it to report intake air flow to the ECM from terminal "C". You've made you last run, and have finished stomping Mousetanks and Ricers for the day, and put the car away. The engine is turned off, and the ECM immediately turns off the MAF power relay. Eight seconds later, providing the fuel pump circuit has shut down, the ECM energizes the MAF burnoff relay, supplying B+ to both terminals "E" and "D". The ECM detects a constant voltage signal from terminal "C" as the hot wire in the MAF is heated to burn off contaminants in preparation for the next *****-stomping day. After a few seconds of burnoff, the ECM de-energizes the MAF burnoff relay, removing power from the MAF entirely. If the ECM does not detect the constant voltage signal on terminal "C" during the period the burnoff relay is energized, the error code will set and be displayed at the next engine start.

This process works millions of times daily on millions of vehicles around the world. Statistically, something has to hit the fan sooner or later.

Look back at the oil pressure sensor on the diagram. The sensor was installed to provide a backup power supply to the fuel pump in the unlikely event of a fuel pump relay failure. It does this thankless job, innocently enough, like a back-up quarterback sits on the bench during every game, just in case... Pretty soon, it gets bored, and devises a method to get attention.

If the pressure switch were to stay on just a little longer than it should, the circuit that was installed to provide backup power to the fuel pump would suddenly provide an alternate source for the MAF power relay. The factory understood this, so the burnoff function is held off until after the fuel pump circuit is de-enrgized. Even though the key is turned off, the latent oil pressure and sluggish switch can briefly close again, and will close the relay, applying power to the MAF on terminal "E", but preventing power from the now-energized MAF burnoff relay from reaching the MAF on terminal "D". The ECM knows that it has turned on the MAF burnoff relay, but doesn't detect a signal from the MAF terminal "C". Thus the code is set, and long after the cycle has completed, the oil pressure switch relaxes enough to open, standing innocently on the sidelines again. The oil pressure switch can be tested, and is presumably good since it is open with no pressure and closed with pressure. Everyone is confused, and parts start getting replaced. Just like the backup quarterback, the starter gets cut and replaced, while the backup sit quietly on the bench.

Factors that contribute to this "NFL-hell" are sludge buildup in the oil pressure switch or gallery in the rear of the block leading to the switch, thicker oils, poor internal oil flow from restrictive bearings or improperly installed cam bearings, and excessive oil pressure damaging teh auxilliary switch.

Another hint to listen for is the fuel pump running after the key is shut off. While this is normal for TPI cars, excesive run-on can be a sign of the problems described above. If the pump runs more than 5-8 seconds with a brief stop between, you might be looking for a new quarterback.

I know this is long and confusing, so in essence, check the oil pressure switch for the fuel pump circuit just for grins.

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Later,
Vader
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"Make Me Bad"
Adobe Acrobat Reader 4.0

[This message has been edited by Vader (edited September 22, 2000).]

 

Thanks for the replys. Well after my hard evening at work to pay towards necesscities for the car (gas, insurance, relays) The code didnt throw. So off came the peice of electrical tape covering the SES light (It really bothers me) and hopefully I can forget about it, but Ill check on that oil pressure switch and keep a watchful eye out for anything unusual. Also, as usual, very informative post Vader, you sound like a few engineers Ive made acquaintance with.

Thanks Again,
Martin

 

Ok, so you are saying high oil pressure can set off error code 36? Well, I get this alot with 34 and my oil pressure is always right below 60 due to a higher pressure pump installed by the previous owner. Am I getting all worked up over nothing? Does it not work like that? Thanks..again You really are alot of help

 

This time with a signature..

Ok, so you are saying high oil pressure can set off error code 36? Well, I get this alot with 34 and my oil pressure is always right below 60 due to a higher pressure pump installed by the previous owner. Am I getting all worked up over nothing? Does it not work like that? Thanks..again You really are alot of help

------------------
-Red '88 IROC 5 Speed TPI
-Dual Friction Centerforce Clutch
-Accel 300+ Racing Ignition
-Accel 300+ Pro Sleeve Plug Wires
-Accel U-Grove Plugs
-Flowmaster Force II 3 Chamber Cat Back Exhaust
-Hypertech Chip
-Hypertech Airfoil
-Removed MAF Screens
-Gutted Air Box
-Best E/T 14.90(bald tires, SES light on)
-Best MPH 92.4(bald tires)

 

can this code also cause the maf to read funny? With my ALDL, my camaro reads fine, my friends was staying around 9 Grams per sec. , is this related?It wuold go al ot higher but drop back down, like on the freeway it was reading really realy low

 

Iroc_Z28, how is the transmission related to getting a Code 36? If there is something I can check, please give me a hint! My automatic trans equipped '88 IROC has had a code 36 for 9 months now and it comes and goes.

Lately, it happens everytime I start my engine. Even after clearing the engine codes, code 36 returns.

I have changed the burnoff relay and other relays, changed the oil pressure switch, and made sure my MAF connector is a good connection. None of these have helped.

 

Still, no one explains how the transmission shift is related to a Code 36.

 

To further bump this thread, I just messaged about getting my Invoice, so I can get the window sticker and such for my 87.


Thank you....... I will update if they reply.