Code 42

[Electra_T_Type]

So my junkyard fuel pump works (:D) but now the car runs not so great and gives me
Code 42 - Bypass or Electronic Spark Timing (EST) circuit
What is this, and how is it fixed?

[notsoslimshady76]

http://www.w-body.com/index2.html

Stole that from my other online home, w-body.com

[Pilrulz]

I'm pretty sure that means the crankshaft position sensor, but I could be wrong...

[85_Ciera_Rebuild]

Code 42 - Bypass or Electronic Spark Timing (EST) circuit
What is this, and how is it fixed?

I have no idea which motor you have, but from 87 Olds shop manual (2.8L engine)

Code 42 means the ECM has seen an open or short to ground in the EST or bypass circuits.

First Test:

Clear Codes (disconnect battery for 20 seconds or pull ECM fuse)

Idle Engine For 1 minute or until Code 42 Sets.

Does Code 42 Set? (Yes or No???).

[Electra_T_Type]

Car is '87 Century 3.8

[85_Ciera_Rebuild]

Car is '87 Century 3.8


Same procedure, for step one, but idle for 2 minutes, after clearing code.

[CieraSL92]

It does not mean Crank sensor. That is one of several parts that drive the Electronically controlled spark ignition. Without it functioning, the car would not start at all.

For the diagnosis, yeah, ditto on what 85 said. This code also indicates that the computer will not advance or retard timing, and will run on a fairly primitive spark table, hence why poor performance and (possibly) a poor idle.

Did you disturb any wiring in the engine compartment? I've seen this a couple times and it's almost always literally a chafed wire rubbing up against the coil pack support bracket.

[Electra_T_Type]

Yes, the car is very hard to start, about 30 seconds of cranking to get it going and then very poor idle and driveability issues. It was running fine before the fuel pump went out...
Another thing to note is that after my mechanic replaced my transmission the car woulden't start, and he got it going but I know he diden't know what the hell he was doing and such I've found some poorly puttogether stuff (Relays lying around, neutral switch not hooked up, etc).

[85_Ciera_Rebuild]

car is very hard to start...then very poor idle and driveability issues...

1. Check rail fuel pressure...it has to be within specs...if your used fuel pump can not achieve 34-40 psi, you will have driveability issues.

2. Fuel Pump Relay - On GM vehicles I'm aware of, when you turn key-switch to On position, the ECM activates a Fuel Pump Relay for a few seconds.

Hence, turn key-switch on, and listen...if this circuit is not working, then your vehicle may have only an oil pressure switch for turning on fuel pump, which means you have to get enough oil pressure to turn on fuel pump.

3. Code 42 Test - What was the result...Yes/No...did Code 42 show up again after idling?

[Jr's3800]

Here is the Code 42 for the 87 Buick Century 3.8 Vin 3




Hope that helps

[Zaloryan]

I'm sure somebody else has a Haynes Manual specific to their car, but if someone needs, I can scan out all the trouble codes for a 1990 Cutlass Ciera.

[turbokinetic]

Here is another reference sheet found on the net. Two times I've seen this code set because the connector on the end of the ignition module had issues (where the main harness plugs in).
Once the connector was wet; the other time the terminals has been "probed" and spread open. They did not grip the pins in the module.
Wet connector caused horrible drivability and stalling; the other one had no power but ran OK otherwise.
Harness tends to chafe on the 3.8 / 3800 engines where it goes behind the steering pump, too you might look there.

--------------------------------------------

CODE 42

Trouble Code 42 indicates that there may be a malfunction in the Electronic Spark Timing (EST) system.

During cranking, the timing is controlled by the ignition module while the ECM monitors the engine speed. When the engine speed exceeds 400 RPM, the ECM sends a BYPASS signal to the ignition module which switches the timing to ECM control. The ECM calculates what the timing should be then "tells" the ignition module via the EST circuit.

An open or ground in the EST circuit will stall the engine and set a Code 42. The engine can be re-started but it will run on ignition module timing.

The conditions for setting this code are:

System in BYPASS mode but the ignition module is still controlling timing

- or -
Engine speed > 600 RPM with no EST pulses (ECM controlled timing) going to the ignition module for 200 msec.



Typical causes for this code include:

1) BYPASS line is open or grounded
2) EST line is open or grounded
3) PROM or CALPACK not seated properly in the ECM
4) Poor connections between ignition module and ECM
5) Poor routing of EST harness and/or poor quality ignition wires (EMI induced electrical noise)
6) Faulty or incorrect ignition module
7) Faulty ECM

[85_Ciera_Rebuild]

about 30 seconds of cranking to get it going and then very poor idle and driveability issues.


What is fuel pressure at idle, and with vacuum line disconnected at pressure regulator?

[85_Ciera_Rebuild]

Yes, the car is very hard to start


Any update?

[Electra_T_Type]

Any update?

Coil pack and ICM tested good, interestingly the ICM must have been replaced by my mechanic when the trans was changed cause its a Wells part.
Since I finally got a damn job I'm going to try the crank sensor next.

[85_Ciera_Rebuild]

Coil pack and ICM tested good.

Do you have (or can get) a high impedance volt meter?

If you can find that By-Pass Circuit wire (424), you could see if it is getting the 5 Volt signal.

On 1987 Olds at Comuter, its the Tan/Blk-striped (Solid Tan, with Black stripe) wire is where you would want a volt meter while engine is cranking.

This is a diagnostic "choke" point.

From Jr's3800's post:

[CieraSL92]

This is most likely a wiring issue, not a sensor issue. I have yet to see a bad CPS set a code (though i believe there is one for it). In my experience, they typically do not work at all (no spark) or when the sensor is heat-soaked the motor stalls and will not restart until it's cooled.

[Electra_T_Type]

Damn I hate wiring, I don't have a volt meter or let alone know how to use one, hmm I may have to dig deeper for a broken wire.

[Pontiac6ksteawd]

This sounds erily like the cam shaft sensor has gone bad. Which is a known problem on the first gen 3.8. My Toronado had the same problem, althou I dont remember the code. And yes, the 3.8's do have cam shaft sensors. The sensor doenst go bad, put the magnetic pickup on the cam sprocket does. But this is just my opinion..

[Electra_T_Type]

Well I gave it and took it to a shop and they said the fuel pump so they replaced it (I had one lying around for my Park Ave) and now its mobile but running crummy, I suspect a MAF, or O2 Sensor issue....

[85_Ciera_Rebuild]

Well I gave it and took it to a shop and they said the fuel pump so they replaced it (I had one lying around for my Park Ave) and now its mobile but running crummy, I suspect a MAF, or O2 Sensor issue....

Did they check rail fuel pressure....if pump pressure and fuel regulator are not up to specs...well, guess what...stuff happens.

[Electra_T_Type]

Did they check rail fuel pressure....if pump pressure and fuel regulator are not up to specs...well, guess what...stuff happens.
Yeah that how they determined it was the pump apposed to a ignition problem. The pump I gave them was a brand new one that was supposed to be for my Park Avenue.

[Electra_T_Type]

Under closer inspection several vacuum lines are falling apart in my fingers, will replace those and report back.

[CieraSL92]

I assume code 42 went away or you wouldn't be going after the vacuum lines?

[centurycoupe]

u said the mech replaced your ignition module? a new or used one? i got code 42 after a stall and it was ig module,replaced with used and went ok 4 a while, then again stalling.went thru 3 of em .wheres the one he took off?check ur connection from there,if its used they heat up and fail intermittently.

[Electra_T_Type]

I assume code 42 went away or you wouldn't be going after the vacuum lines?
Yes diden't show up when I drove from the shop, I'm assuming because the car wasen't getting good fuel pressure.


u said the mech replaced your ignition module? a new or used one? i got code 42 after a stall and it was ig module,replaced with used and went ok 4 a while, then again stalling.went thru 3 of em .wheres the one he took off?check ur connection from there,if its used they heat up and fail intermittently.

New one, the 42 is gone, I wish I knew what he did with it, but he went out of buisness after my car I can see why.
But the car is running crappy, reminds me of how it was running when the O2 Sensor went out 2 1/2 years ago.
Heres a pic from yesterday

[85_Ciera_Rebuild]

But the car is running crappy...

When motor is cold, disconnect the battery for 20 seconds...then drive it for awhile "gently."

Once the battery is disconnected, it uses default map....until O2 sensor puts in some data points to be used. After O2 sensor puts in these data points, it should run better.


If you have a 3.8 motor, on the fuel rail is a Schrader valve; open the cap, get a tire pressure gauge, start the motor up cold, and then shut off the motor, then read the pressure, then in five minutes, read the pressure. Key Word: Cold Motor

If you can take a pressure reading this way, without spilling gas....try it when motor is running. What is pressure reading(s)?

[Pontiac6ksteawd]

Tire pressure guage wont work. The schrader valve is it big for that.

[CieraSL92]

You could just disconnect the O2 sensor totally and performance/idle won't suffer, but gas mileage will. It will stay in open loop. Just for diagnostic purposes, obviously.

Oh just for kicks, with the engine on and running like shit, jump the two diagnostic terminals that you do to get the codes. Does the SES light blink rapidly or slowly?

Edit: that can be used on all a-bodys with MPFI I believe. Slow blinking indicates the computer is in closed loop, rapid indicates open. Don't remember where I read this from, but i believe it was a service manual. Works on mine.

[85_Ciera_Rebuild]

Tire pressure guage wont work. The schrader valve is it big for that.

I use R-12 gauge to check it when on vehicle....and when off vehicle, I hookup the shop air hose to fuel rail and check pressure regulator via using a metered pressure in 30-35 psi range for those type of vehicles.

Sometimes, pawn shops have these old R-12 gauges with hoses real cheap...