Code 157

[huskyfan23]

I pulled codes today and pulled a 157 which says the MAF isn't getting proper voltage. I unplugged it and read 12.32 volts with a multimeter, seems sufficient. I tried hooking my stock MAF up and got the same code. Cleaned them both, same thing. I don't get a CEL, but I shouldn't be pulling any codes. I ran a search and didn't find any answers. People replaced their MAF's and don't pull the code anymore, but I've got 2 perfectly good units with no CEL. Ideas?

 

[Runnin'OnEmpty]

HF23, the 157 code refers to the MAF signal voltage being too low. The 12.32v you read was the battery voltage.

Have you cleared the code, and checked to see if it returns? Maybe it's an old code that's been remedied, since the CEL dosen't light up......

 

[huskyfan23]

Yeah I cleared the codes. I used the multimeter on the + and - prongs of the plug. Should I ground at the plug and read the voltage of the 2 signal wires? What are the specs?

 

[Runnin'OnEmpty]

OK, just checked this in my Haynes manual. The signal terminal is the one on the opposite end of where you checked the battery voltage. The book says you have to re-connect the connector, and backprobe the terminals. Signal and Ground. (Two middle terminals are listed as grounds). With engine running, voltage should be .5-.7v at idle. When engine is revved, the voltage should increase to about 1.5-3v.......

 

[Runnin'OnEmpty]

HF, there's one other test: Disconnect the MAF connector and using an ohmmeter, probe the MAF signal and negative/ground terminals. If you read an open circuit, then the hot-wire element inside the sensor has been damaged.

 

[huskyfan23]

Where'd you find this information in your Haynes? I've got one and couldn't find anything about the MAF. I scanned with the engine off; KOEO, so why does the vehicle need to be running to check voltage if the scanner checked it with the engine off? How do I backprobe? Does that mean plugging it in and check voltage using the wires, or do I have to pull voltage from the pins on the MAF itself? If so, how would I do that with the connector plugged in?

 

[Runnin'OnEmpty]

My Haynes is for 91-01 models; MAF info is on page 6-15. (You might have an earlier edition???)

The test with the engine running has to be done with the connector plugged in. I use straight pins to backprobe with. Just push them into the plug to touch the metal portion, and take the reading off the pin ends. The MAF has to be plugged in and functioning, to be able to send a signal voltage. The signal voltage will increase as the rpms increase, if the MAF is OK.

The ohmmeter test is done with the MAF unplugged and key off. The meter probes will go onto the sensor side of the connector (signal and ground terminals). You're just checking to see if the heater wire is broken. If it's OK, then the meter should read some resistance, if it's bad you'll read an open.

This is a tough one, since the CEL usually comes on with this code.......

 

[huskyfan23]

Wow, I have a much earlier edition, '91-'95. Thanks, I'll try these tests tomorrow.

 

[MrShorty]

Is your 157 a KOEO or continuous memory (CM) code? I would assume CM, since my code list doesn't list a 157 asa KOEO code. If it is a CM code, do you get any codes from the KOER test? Did it pass the KOEO test?
And, be sure to note that codes point to circuits, not sensors. A CM 157 (for example) could just as easily be a result of a loose/broken connection between the MAF and the PCM.

 

[huskyfan23]

Is your 157 a KOEO or continuous memory (CM) code? I would assume CM, since my code list doesn't list a 157 asa KOEO code. If it is a CM code, do you get any codes from the KOER test? Did it pass the KOEO test?
And, be sure to note that codes point to circuits, not sensors. A CM 157 (for example) could just as easily be a result of a loose/broken connection between the MAF and the PCM.

I pulled 157 from a KOEO test. I get a 10 (pass) with KOER. It is a continuous memory code.

 

[MrShorty]

10 isn't a pass code, that's how some code readers report separator pulses and DRT ("goose") pulses. Pass code should be 111.

 

[huskyfan23]

Yeah I meant 111. Anyways, it seems I cleared the codes wrong so now I'm not getting that code even after running the engine. Seems fixed.