AboutRagu Expertise I`ve been with ford for 17 yrs, there is not to much I don`t know. I have 3 masters with ford linc,merc. Iwas a touble shooter for the last 8 yrs
Question Ran KOEO gave 111 pass then the 157 CM code, then ran KOER gave 998 then 157. Check for corroded pin/s on the senor and even installed a new MAF sensor still same condition. I checked along the harness for damage, none. Checked for corrosion on TPS sensor, nothing, pulled the PCM plug also no corrosion. Curious to get your thoughts on replacing the PCM or trying something else.
Answer 99.% of the time a PCM WILL NOT BE THE PROBLEM .Continuous Memory Diagnostic Trouble Code (DTC) 157 indicates the Mass Air Flow (MAF) sensor signal went below 0.4 volt sometime during the last 80 warm-up cycles.
Possible causes:
Poor continuity in MAF sensor harness or connectors.
Intermittent open or short in MAF sensor or harness.
Damaged MAF sensor.
Idle Air Control (IAC) system failure (at closed throttle position).
Clear continuous memory. See: Reading and Clearing Diagnostic Trouble Codes\Clearing Diagnostic Trouble Codes
Start engine and idle for 5 to 10 minutes.
Vehicle in "PARK" or "NEUTRAL".
Suddenly goose (greater than a half second) the throttle, approaching 1500 rpm.
Allow to return to idle.
Then, goose the throttle again, approaching 1500 rpm.
Key "ON", engine "OFF".
Run Self-Test to observe Continuous Memory DTCs.
Is Continuous Memory DTC 157 present
Key "OFF".
Disconnect sensor.
Disconnect Powertrain Control Module (PCM) . Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.
Install breakout box, leave PCM disconnected.
Measure resistance between VPWR circuit at the Mass Air Flow (MAF) sensor vehicle harness connector and test pins 37 and 57 at the breakout box.
Measure resistance between MAF circuit at the MAF sensor vehicle harness connector and test pin 50 at the breakout box.
Is each resistance less than 5.0 ohms? IF YES THEN DO NEXT STEP IF NOT LET ME KNOW
Key "OFF".
Mass Air Flow (MAF) sensor disconnected.
Breakout box installed, Powertrain Control Module (PCM) disconnected.
Measure resistance between test pin 50 and test pins 9, 40 and 60 at the breakout box.
Is each resistance greater than 10,000 ohms? IF YES THEN DO NEXT STEP IF NOT LET ME KNOW
Key "OFF".
Mass Air Flow (MAF) sensor disconnected.
Breakout box installed, Powertrain Control Module (PCM) disconnected.
Measure resistance between PWR GND circuit at the MAF sensor vehicle harness connector and battery negative post.
Is resistance less than 10 ohms?
LET ME KNOW
